atom

[yuán zǐ]

physical concept

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Atom chemical reaction Indivisible fundamentals particulate 。 Atoms are inseparable in chemical reactions, but Physics Status can be split. Atoms are composed of Nucleus And moving around the nucleus Electronics form. The smallest unit of an atom that constitutes a general substance is called element 。 There are 118 known elements.^[1-2] Therefore, it has a core structure.

Chinese name: atom
Chemical name: atom

Physical name: atomy
Definition: Basic particles that can not be separated again in chemical reaction
Nature: Never stop doing irregular sports

catalog

seven Atomic substance
eight The difference between atoms and ions
nine Origin and current situation
▪ Nucleosynthesis
▪ earth
▪ Rare and theoretical form
ten Atomic radius
eleven magnetic

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Atomic model (14 sheets)

Atoms are chemical reaction Indivisible minimum particulate 。 A positive atom contains a compact The nucleus of Nucleus Electrons with negative charge around them. The nucleus of a negative atom is negatively charged, and the surrounding electrons are positively charged. The nucleus of a positive atom consists of a positively charged proton And electrically neutral neutron form. The antiproton in the nucleus of a negative atom is negatively charged, thus making the nucleus of a negative atom negatively charged. When the number of protons is the same as the number of electrons, the atom is Electroneutrality Of; Otherwise, it has positive charge perhaps negative charge Ions of. The type of atom varies according to the number of protons and neutrons: the number of protons determines which element the atom belongs to, while the number of neutrons determines which element the atom belongs to isotope 。^[3] Atoms form molecules, while the same kind of charges in molecular components repel each other, and different kinds of charges attract each other.

The atomic diameter is about 10 ⁻ ⁻ ¹ m. The atomic mass is extremely small, and its order of magnitude is generally 10 -27 kg， Quality is mainly concentrated in proton and neutron On. There are electrons outside the nucleus, electrons transition produce spectrum , electrons determine the chemical properties of an element, and magnetic It has a great impact. All atomic elements with the same proton number, each element mostly has an unstable isotope, which can Radioactive decay 。

Atoms were first philosophically endowed with Ontology With the progress of human understanding, the abstract concept of meaning has gradually changed from an abstract concept to a scientific theory. The nucleus and electrons belong to Microparticle , constitute atoms. And atoms can form molecules.

Encyclopedia x Knowledgeable: Illustration of Particles

definition

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The smallest particle in a chemical change.

Note: "Atom is the smallest particle of material" is wrong. Atom can be divided into nucleus and extranuclear electrons. The nucleus is composed of protons and neutrons, and the number of protons is the basis for distinguishing different elements.

Protons and neutrons can continue to be subdivided. So atoms are not the smallest particles that make up matter, but atoms are the smallest particles in chemical reactions.

Development history

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Early history

The concept that matter is composed of discrete units and can be arbitrarily divided has been circulated for thousands of years, but these ideas are only based on abstract, philosophical reasoning, rather than experiments and experimental observations. With the passage of time and the change of culture and school, the nature of the atom in philosophy has also changed greatly, and this change is often accompanied by some spiritual factors.

Nevertheless, the basic concept of atom is still adopted by chemists thousands of years later, because it can concisely explain some phenomena in the chemical world.

Atomism yes Elementalism It is the most concise and scientific form of theory. Dampier, a British historian of natural science, believes that atomism is "closer to modern ideas than any theory before or after it" in science. The founder of atomism is ancient Greek people leucippus (500~440 BC), he was Democritus Our teacher. When ancient scholars talked about atomism, they usually mixed their theories together. Lukiber's theory was developed and improved by his student Democritus, so Democritus is recognized as the main representative of atomism.

Democritus It is believed that the origin or fundamental element of all things is "atom" and "void". "Atom" means "indivisible" in Greek. Democritus uses this concept to refer to the most basic material particles that constitute concrete things. The fundamental characteristic of an atom is "full and solid", that is, there is no gap inside the atom, it is solid, inaccessible, and therefore inseparable. Democritus believed that the atom is eternal, immortal; Atoms are infinite in number; The atom is in constant motion, and its only form of motion is“ Vibration ”Atoms are tiny and invisible to the eyes, that is, they cannot be perceived by the senses and can only be understood by reason.

Encyclopedia x ignorance: illustration Democritus

After more than 20 centuries of exploration, scientists confirmed the real existence of atoms through experiments from the 17th century to the 18th century. British chemist in the early 19th century J. Dalton On the basis of further summarizing the experience of predecessors, the atomic theory with modern significance was put forward. This atomic theory created a new era of chemistry. He explained many physical and chemical phenomena.

atom It is the smallest unit of an element that can maintain its chemical properties. An atom contains a dense nucleus and a number of Nucleus Electrons with negative charge around them. The nucleus consists of a positively charged proton And electrically neutral neutron form. Atoms are the smallest particles of chemical change, molecules are composed of atoms, and many substances are directly composed of atoms.

The English name of the atom is derived from Greek and originally meant to be indivisible. Long ago, Greek and Indian philosophers put forward the concept of indivisibility of the atom. In the 17th and 18th centuries, chemists discovered the basis of physics: for some substances, they cannot be further decomposed by chemical means. In the late 19th and early 20th centuries, physicists discovered that Subatomic particle And the internal structure of the atom, which proves that the atom is not unable to be further divided. quantum mechanics The principle can provide a good model for atoms.

modern history

In 1661, natural philosopher Robert Boyle Published《 The Sceptical Chemist 》（ The Sceptical Chymist ）He believes that matter is composed of different "particles" or free combination of atoms, rather than basic elements such as air, earth, fire and water. Engels It is believed that, Boyle Is the first chemist to establish chemistry as a science^[4] 。

In 1789, French scientist Lavoisier The word atom was defined. Since then, atom has been used to express Chemical change The smallest unit in.

Atom described by Dalton in New System of Chemical Philosophy

In 1803, English teachers and natural philosophy home John Dalton （ John Dalton ）The concept of atom is used to explain why different elements always react in integral multiples, that is Multiple ratio law （ law of multiple proportions ）； It also explains why some gases are more soluble in water than others. He proposed that each element contains only one atom, and these atoms combine to form a compound.

In 1827, British botanist Robert Brown （ Botanist Robert Brown ）When observing the dust on the water surface with a microscope, we found that they were moving irregularly, which further proved the particle theory. Later, this phenomenon was called Brownian motion 。

In 1877, Desholkes （ J. Desaulx ）Propose Brownian motion Is due to the water molecule Thermal movement Caused by.

In 1897, on Cathode ray Physicists Joseph Thomson （J.J.Thomsom） Discovered the electron and its Subatomic The idea that atoms can no longer be separated has been shattered by their properties. Thompson believes that electrons are evenly distributed on the whole atom, just as they are scattered in a uniform ocean of positive charges, and their negative charges cancel out those positive charges. This is also called Eccles cake Model (date stone model).

In 1905, Einstein The first mathematical analysis method is proposed, which proves that Desholkes Guess.

In 1909, a physicist Ernest Rutherford （ Ernest Rutherford） Under the guidance of, Philip Leonard （ P.E.A.Lenard ）Bombard gold foil with helium ions. It is found that the deflection angle of a small part of ions is far greater than the predicted value using Thomson hypothesis. Rutherford pointed out that most of the mass and positive charge in the atom are concentrated in the center of the atom Nucleus In the middle, electrons are like planet It surrounds the nucleus as it surrounds the sun. belt positive electricity When the helium ion of 20% passes through the vicinity of the atomic nucleus, it will be reflected at a large angle. This is the nuclear structure of the nucleus.

In 1913, during the experiment on radioactive decay products, radiation chemists Frederick Soddy （ Frederick Soddy ）Find out about periodic table of ele ments There is often more than one mass number of atoms at each position in the. Margaret Todd created isotope The word "" refers to different kinds of atoms in the same element. During the research on ionic gas, Thompson invented a new technology that can be used to separate different isotopes, which eventually led to the discovery of stable isotopes^[5] ； In the same year, physicists Niels Bohr （ Niels Bohr ）Look again rutherford He believed that the electron should be located in the orbit determined in the atom and be able to jump between different orbits, instead of being free to move inward or outward as previously thought. When electrons transition between these fixed orbits, they must absorb or release specific energy. such Electron transition The fixed position lines in the hydrogen atom spectrum can be well explained by the theory of^[6] , and set Planck constant And Atomic hydrogen spectroscopy Of Rydberg constant Got in touch.

In 1916, German chemist Kossel （ Kossel ）After investigating a large number of facts, we come to the conclusion that the atoms of any element must make the outermost layer meet the 8-electron stable structure^[7] 。 Louis find Chemical bond Its essence is the interaction of electrons between two atoms.

In 1919, physicist Rutherford Alpha particle Protons found in the experiment of bombarding nitrogen atoms^[8] 。 Francis William Aston （ Francis William Aston ）Using mass spectrum It is confirmed that isotopes have different masses, and the mass difference between isotopes is an integer, which is called the integer rule. American chemist Owen Langmuir It is proposed that the electrons in atoms are connected or aggregated with each other by certain properties. A group of electrons occupies a specific Electronic layer 。

1923, American chemist Gilbert Newton Lewis （ G.N.Lewis ）Developed Cosell's theory and proposed covalent bond Electron pair theory^[7] 。 Lewis hypothesis: in a molecule, an electron from one atom and an electron from another atom form an "electron pair" between atoms Chemical bond 。 This was a hypothesis that ran counter to orthodox theory at that time, because Coulomb's law It shows that the two electrons are mutually exclusive, but Lewis's assumption was soon accepted by the chemical community, which led to the proposition of the hypothesis of the opposite spin of the electrons between atoms^[9] 。

In 1926, Schrodinger （ Erwin Schrödinger ）Using Louis de Broglie （ Louis de Broglie ）Proposed in 1924 Wave particle duality A mathematical model of the atom is established to describe the electron as a three-dimensional waveform. But in mathematics, it is impossible to obtain the exact values of position and momentum at the same time. Werner Heisenberg （ Werner Heisenberg ）The famous Uncertainty principle 。 This concept describes that for a measured position, only an uncertain range of momentum can be obtained, and vice versa. Although this model is hard to imagine, it can explain some previously observed but unexplainable properties of atoms, such as those of atoms larger than hydrogen Spectral line 。 Therefore, people no longer use Bohr's atomic model, but regard the atomic orbit as the region where electrons appear with high probability (electron cloud)^[10] 。

mass spectrum The invention of the invention allows scientists to directly measure the accurate mass of atoms. The device uses a magnet to bend a beam of ions, and the amount of deflection depends on the mass charge ratio of the atom. Francis William Aston The mass spectrum proves that isotopes have different masses, and the mass difference between isotopes is an integer, which is called Integer rule 。

In 1930, scientists found that, Alpha ray When bombarding beryllium-9, a Electroneutrality , rays with extremely strong penetrability. Initially, this was thought to be Gamma ray 。

In 1932, Curie, Jorio The couple found that this kind of radiation can paraffin wax Hit protons in; In the same year, Rutherford's students James Chadwick （ James Chadwick ）It's supposed to be neutrons^[8] , and isotope Is redefined as an element with the same proton number and different neutron number.

In 1950, with Particle accelerator And the development of particle detectors, scientists can study High-energy particle Collision between. They found that neutrons and protons are a kind of hadrons quark Particulate composition. With the development of the standard model of nuclear physics, it can successfully explain the interaction between the whole atomic nucleus and subatomic particles at the subatomic level.

In 1985, Chu Diwen And colleagues in Bell Laboratories A new technology has been developed that can use lasers to cool atoms. William Daniel Phillips The team managed to place sodium atoms in a magnetic trap. These two technologies, together with a method developed by Claude Koen Donudri's team based on the Doppler effect, can cool a small amount of atoms to a temperature range of micro Kelvin, so that atoms can be studied with high accuracy Bose Einstein condensation The discovery of^[11] 。

Historically, a single atom was considered too small for scientific research. In 2012, scientists have successfully connected a single metal atom with an organic ligand to form a single electron transistor. In some experiments, by Laser cooling These experiments can lead to a better understanding of matter.

History

Dalton's atomic model

British natural scientist John Dalton Transforming the speculative atomic theory of ancient Greece into a quantitative chemical theory, he put forward the first theoretical model of atoms in the world. His theory mainly includes the following four points^[7] ：

① All matter is made up of very small, indivisible matter particles, that is, atoms.

② The atoms of the same element have the same properties and masses, while the atoms of different elements have different masses.

③ Atoms are tiny, indivisible solid spheres.

④ Atoms are participants Chemical change Minimum unit of, at chemical reaction In, atoms are merely rearranged, not created or disappeared.

Although it has been confirmed by later generations that this is a failed theoretical model, Dalton first brought atoms from philosophy into chemical research, which has clearly defined the direction of future chemists' efforts. Chemistry really starts from the ancient alchemy Dalton was therefore hailed as the "father of modern chemistry".

Raisin pudding model (jujube cake model)

The raisin pudding model (date cake model) was proposed by Thompson, which is the first time that there is a atomic structure The atomic model of.

Thomson proposed the raisin pudding model of the atom based on the discovery of electrons（ Jujube stone model ）， Thomson think^[7] ：

① The positive charge is evenly distributed in the atom like a fluid, and the electrons are distributed like raisins positive charge Their negative charges cancel out those positive charges.

② When excited, electrons will leave the atom and produce Cathode ray 。

The experiment of alpha particle bombarding gold foil completed by Rutherford, a student of Thomson（ Scattering experiment ）, denied the raisin pudding model（ Jujube cake model ）Is correct.

Saturn model

In the same year that Thomson proposed the raisin pudding model, Japanese scientists proposed Saturn model It is believed that the electrons are not uniformly distributed, but concentrated on a fixed orbit around the nucleus^[12] 。

Planetary model

The planetary model is composed of rutherford In proposing to Classical electromagnetism As the theoretical basis, the main contents are^[7] ：

① Most of the volume of an atom is empty.

② In the center of the atom there is a very small and extremely dense nucleus.

③ All the positive charges of the atom are in the nucleus, and almost all the mass is concentrated in the nucleus. The negatively charged electrons move around the nucleus at high speed in nuclear space.

With the progress of science, Linear spectrum of hydrogen atom The fact that the planetary model is not correct.

Bohr's atomic model

To explain hydrogen The fact that atomic linear spectrum, rutherford Bohr, a student of, accepted Planck's quantum theory and Einstein's photon concept, and proposed the atomic structure model of the layered arrangement of extranuclear electrons on the basis of the planetary model. Bohr atomic structure model The basic idea of^[13] ：

Bohr's atomic model

① The electron in an atom is in a circular orbit with a fixed radius（ orbit ）It moves up around the atomic nucleus and does not radiate energy.

② Electrons moving in different orbits have different energies (E), and the energies are quantized. The orbital energy value increases with the increase of n (1, 2, 3,...), and n is called Quantum number 。 Different orbits are named K (n=1), L (n=2), M (n=3), N (n=4), O (n=5), P (n=6), Q (n=7) respectively.

③ When and only when the electron is from an orbit transition It will not radiate or absorb energy until it reaches another orbit. If the radiant or absorbed energy is expressed in the form of light and recorded, a spectrum is formed.

Bohr's atomic model well explains the Linear spectrum However, it is powerless to deal with more complex spectral phenomena.

Modern quantum mechanical model

physical scientist De Broglie 、 Schrodinger and Heisenberg After 13 years of hard demonstration, the modern quantum mechanical model has well explained many complex spectral phenomena on the basis of the Bohr atomic model, and its core is Wave dynamics 。

In Bohr atomic model, the orbit has only one quantum number (main quantum number), and modern quantum mechanics model introduces more quantum numbers（ quantum number ）^[7]^[13] 。

① Principal quantum number （ principal quantum number ）, the principal quantum number determines different Electronic sublayer , named K L、M、N、O、P、Q。

② Angular quantum number ( angular quantum number ）, the angular quantum number determines different energy levels, the symbol "l" has n values (0, 1, 2, 3,... n-1)^[20] The symbols are s, p, d, f, g, indicating that for multi electron atoms, the motion state of the electron is related to l.

③ Magnetic quantum number （ magnetic quantum number ）The magnetic quantum number determines the orbits of different energy levels, with the symbol "m" (see "magnetic moment" below). Useful only when applied magnetic field. The three quantities "n", "l" and "m" determine the motion state of an atom.

④ Spin magnetic quantum number （ spin m.q.n. ）The electron in the same orbit has two spins, namely, the essence of the "↑↓" spin phenomenon is still under discussion.

Basic composition

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Subatomic particle

Compound atom nucleus proton quark

Although the English name of the atom（ atom ）It is meant to be the smallest particle that cannot be further divided. However, with the development of science, atoms are considered to be composed of electrons, protons and neutrons (hydrogen atoms are composed of protons and electrons), which are collectively called subatomic particles. Almost all atoms contain the above three subatomic particles, but protium (hydrogen isotope) has no neutrons, and its ion (after losing electrons) is just a proton.

The proton has a positive charge, and its mass is 1836 times that of the electron, 1.6726 × 10 ⁻ ² ⁷ kg. However, some of its mass can be converted into atoms binding energy 。 Neutron is not charged. The mass of free neutron is 1839 times that of electron, 1.6929 × 10 ⁻ ² ⁷ kg. The size of neutron and proton is similar, both in the order of 2.5 × 10 ⁻⁻⁻⁻ m, but their surfaces cannot be precisely defined.

Although the atom is very small and cannot be subdivided by chemical methods, it can still be subdivided by other methods, because the atom also has a certain composition. An atom is composed of a positively charged nucleus in the center and negatively charged electrons outside the nucleus (opposite to antimatter). The nucleus is composed of two particles, proton and neutron. The electrons move at a high speed in a large space outside the nucleus.

In physics Standard Model Theory Protons and neutrons are called quark Of Elementary particle Composition. Quark is Fermion It is one of the two basic components of substances. Another basic component is called Lepton The electron is a kind of lepton. There are six kinds of quarks, each with a fractional charge, either+2/3 or - 1/3. The proton is composed of two Upper quark And a Lower quark The neutron is composed of one upper quark and two lower quarks. This difference explains why the charge and mass of neutrons and protons are different. Quarks are composed of Strong interaction Combined by Gluon As an intermediary. Glue is Gauge boson One of them is a kind of basic particle used to transmit force.

The subatomic particles have quantization characteristics and wave particle duality. The formula is: λ=h/p=h/mv, where λ by wavelength , p is momentum, h is Planck constant （ 6.626×10⁻³⁴ J·S)^[14] 。

Electronics

Approaching in an interior vacuum When the glass tube sealed with metal electrodes at both ends is connected with high-voltage direct current, the cathode end will emit cathode rays. The fluorescent screen can display the direction of this ray. If a uniform electric field is applied, the cathode ray will be biased to the anode; If a runner is installed in the glass tube, the ray can make the runner rotate. Later, it was confirmed that cathode rays were a group of high-speed particles with negative charges, that is, electron flow. The electron was discovered^[15] 。

The electron is the first subatomic particle discovered. So far, the electron is the lightest of all particles, only 9.11 × 10 ⁻ ³ ¹ kg, which is the hydrogen atom [1/1836.152701 (37)], which was made by Millikan through the famous "oil drop experiment" around 1910. The electron has a negative charge of one unit, namely 4.8 × 10 ⁻⁻⁹ electrostatic unit or 1.6 × 10 ⁻⁹ coulomb, whose volume is too small to be measured by existing technology.

Modern physics believes that electrons belong to Lepton One of them is material Basic unit One (the other is quark^[16] ）。

Electronic cloud

Electron cloud image of hydrogen atom

Electronics have Wave particle duality We can't affirm that he is at a certain point in space at a certain moment, just as we can describe the motion of ordinary objects. We can only point out the possibility (i.e. the probability) of its appearance somewhere outside the nucleus.

The probability of electrons appearing everywhere in the nucleus is different. Some places have a high probability of appearing, while some places have a low probability of appearing. If the probability of electrons appearing everywhere outside the nucleus is described by small black dots (the greater the probability of appearing, the denser the small black dots), then a slightly intuitive image will be obtained. In these images, the atomic nucleus seems to be enveloped by a cloud of negatively charged electrons, so it is called Electronic cloud 。

In an atom, electrons and protons are Electromagnetic force And mutual attraction is also the force that binds electrons to a static electricity Potential well From this potential well The middle escape requires external energy. The closer the electron is to the nucleus, the greater the attraction. Therefore, compared with the outer electrons, the electrons near the nucleus need more energy to escape.

Wave functions of the first five atomic orbitals

Atomic orbital It describes the probability distribution of electrons in the nucleus Mathematical equation 。 In practice, only a group of discrete (or quantized) orbits exist, and other possible forms will collapse into a more stable form soon. These orbits can have one or more rings or nodes, and their size, shape and spatial direction are different.

Each atomic orbital corresponds to the energy level 。 An electron can jump to a higher energy level by absorbing a photon with enough energy. Similarly, through Spontaneous emission An electron in the high energy state can also jump back to a low energy state, releasing photons. These typical energies, that is, the energy difference between different quantum states, can be used to explain atoms Spectral line 。

Connect the places with equal probability of appearance of electrons outside the nucleus, as the interface of the electron cloud, so that the total probability of appearance of the electron cloud inside the interface is very high (such as 90% or 95%), and the probability outside the interface is very small. There is a space range covered by this interface, called atomic orbit. The atomic orbit here has different meanings from the macroscopic orbit.

The energy required to remove or add an electron in the nucleus is far less than the binding energy of the nucleus. These energies are called Electron binding energy 。 For example: take away the hydrogen atom ground state Electronics only need 13.6eV. When the number of electrons equals the number of protons, the atom is Electroneutrality Of. If the number of electrons is greater or less than the number of protons, the atom will be called an ion. The outermost electrons of an atom can be moved to adjacent atoms or shared by two atoms. It is because of this mechanism that atoms can bond to form molecules or other kinds of compounds, such as ions or covalent network crystals.

The atomic orbitals are Schrodinger equation The Schrodinger equation is a second-order partial differential equation:

(δ²ψ/δx²)+(δ²ψ/δy²)+(δ²ψ/δz²)=-(8π²)/(h²)·(E-V)ψ，

The solution ψ of the equation is a function of x, y, z, written as ψ (x, y, z). In order to describe the meaning of the wave function more vividly, the spherical coordinates are usually used to describe the wave function, that is, ψ (r, θ, φ)=R (r) · Y (θ, φ), where R (r) function is a function related to the radial distribution, called the radial distribution function; Y (θ, φ) is related to the angular distribution, which is called the angular distribution wave function^[14] 。

Nucleus

All protons and neutrons in an atom combine to form a very small nucleus. Together, they can also be called nucleons. The radius of the nucleus is about 1.07 × A ^ 1/3 fm, where A is the total number of nucleons. The atomic radius is about 105fm in order of magnitude, so the radius of the atomic nucleus is much smaller than that of the atom. Nucleons are bound together by the residual force that can work in a short distance. When the distance is less than 2.5fm, the strength is far greater than the electrostatic force, so it can overcome the mutual exclusion between positively charged protons.

The atoms of the same element have the same number of protons, which is also called the atomic number. For a particular element, the number of neutrons can change, which determines which kind of element the atom is isotope 。 The number of protons and neutrons determines which kind of element the atom is nuclide 。 The number of neutrons determines the stability of the atom, and some isotopes can spontaneously undergo radioactive decay. Neutron and proton are both types of fermions. According to quantum mechanics Pauli exclusion principle , there cannot be two identical ones Fermion They also have the same quantum physical state. Therefore, each proton in the nucleus occupies a different energy level, and the situation of neutrons is the same. However, the Pauli exclusion principle does not prohibit a proton and a neutron from having the same quantum state 。^[4]

If the number of protons and neutrons in an atomic nucleus is different, the atomic nucleus is prone to radioactive decay to a lower energy level, and makes the number of protons and neutrons more similar. Therefore, atoms with the same or very similar number of protons and neutrons are less likely to decay. However, when the atomic number gradually increases, more neutrons are needed to stabilize the whole atomic nucleus due to the increased repulsion between protons, which affects the above trend. Therefore, when the atomic number is greater than 20, it is impossible to find a stable nucleus with the same number of protons and neutrons. With the increase of Z, the ratio of neutron to proton gradually tends to 1.5.

Schematic diagram of nuclear fusion, in which two protons fuse to generate a deuterium nucleus containing a proton and a neutron, and release a positron (the antimatter of the electron) and an electron neutrino. The opposite process is Nuclear fission 。^[11]

If the nuclear mass produced after nuclear fusion is less than the total atomic mass before fusion, then according to Einstein Of Mass energy equation These mass differences are released as energy. This difference is actually the binding energy between atomic nuclei, for two atomic nuclei whose atomic number is before iron or nickel.

stay Alpha particle scattering experiment It was found that the mass of the atom is concentrated in a very small and positively charged material, which is the nucleus.

The nucleus, also called nucleon, is composed of all protons and neutrons in the atom. The radius of the nucleus is about 1.07 × A ^ 1/3 fm, where A is the total number of nucleons. Atomic radius The order of magnitude of is about 105fm, so the radius of the nucleus is much smaller than that of the atom.

form

The nucleus consists of protons and neutrons (hydrogen has only one proton), quantum state 。

In different isotopes, the energy required to connect the nucleons together

proton （ proton ）

The proton consists of two Upper quark And a Lower quark Composition, with a unit positive charge, the mass is 1836.152701 (37) times of the electronic mass, 1.6726231 (10) × 10 ⁻ ² ⁷ kg, however, part of the mass can be converted into atomic binding energy. Atoms with the same proton number are the same element, atomic number=proton number= Nuclear charge number =Number of extranuclear electrons^[13] 。

neutron （ neutron ）

Neutron is the subatomic particle with the largest mass in the atom. The mass of free neutron is 1838.683662 (40) times that of electron, 1.6749286 (10) × 10 ⁻ ² ⁷ kg. The size of neutron and proton is similar, both in the order of 2.5 × 10 ⁻⁻⁻⁻ m, but their surfaces cannot be precisely defined.

Neutron is composed of one upper quark and two lower quarks. The charges of the two quarks cancel each other, so the neutron is not sensible. However, it is wrong to think that "neutron is not charged".

For a particular element, the number of neutrons can change. The same element with different neutron numbers is called isotope. The number of neutrons determines the stability of an atom. Isotopes of some elements can undergo spontaneous radioactive decay.

Nuclear force （ nuclear force ）

Nucleus It is bound by a strong force in the area of 10 ⁻⁻⁻⁻ m linear degree. Since protons are positively charged, according to Coulomb's law, the repulsion between protons would have burst the atomic nucleus. However, there is a force in the atomic nucleus that tightly binds protons and neutrons together. This force is called nuclear force. In a certain distance, the nuclear force is far greater than the electrostatic force, which overcomes the mutual exclusion between positively charged protons^[8] 。

The action range of the nuclear force is called the force range. The action range is about 2.5fm, up to 3fm^[8] That is, it cannot extend from one nucleus to another, so nuclear force belongs to short-range force.

nuclide （ nuclide ）

Nuclei with the same number of protons and neutrons are called nuclides, and the number of protons is represented by the x-axis; The image obtained by representing the number of neutrons with the y-axis is called the nuclide graph. It can be found from the graph that when x ∈ {0, 1, 2, 3,..., 20}, the function on the nuclide graph is approximately y=x, but with the increase of the number of protons, the coulomb repulsion between protons is significantly enhanced, and the atomic nucleus needs more neutrons than usual to maintain the undetermined atomic nucleus. When x ∈ {21, 22, 23,..., 112}, The function is approximately y=1.5x, and the number of neutrons is greater than the number of protons^[8] 。

binding energy （ energy of the nucleus ）

In the atomic nucleus, the energy consumed by separating the nucleon from the atomic nucleus to do work is called binding energy. Experiments show that the mass of any atomic nucleus is always less than the sum of the masses of its constituent nucleons (this difference is called Quality loss ）Therefore, the binding energy can be calculated from Einstein's mass energy equation^[8]^[14] ：

Binding energy=(rest mass of all protons and neutrons in the nucleus and - rest mass of the nucleus) × speed of light ^2

Nuclide map

Average binding energy （ binding e.o.t.n ）

The average binding energy of each nucleon in an atomic nucleus is called the average binding energy, and the calculation formula is^[14] ：

Average binding energy of each nucleon=sum total energy ÷ number of nucleons

The greater the average binding energy, the more difficult it is for the nucleus to be decomposed into a single nucleus^[8] 。 It can be seen from the right figure that:

① The average binding energy of heavy nuclei is smaller than that of medium nuclei, so they are prone to fission and release energy.

② The average binding energy of light nuclei is smaller than that of heavier nuclei, so energy will be released when light nuclei fuse^[8] 。

Atomic Vander Waals radius It means that in the molecular crystal Van der Waals Combination, such as Noble gas Half the distance between two adjacent nuclei.

Schematic Diagram of Nuclear Fusion

The number of protons and neutrons in the atomic nucleus can also be changed, but because of the strong force between them, it requires high energy. When multiple particles gather to form a heavier atomic nucleus, it will happen nuclear fusion For example, the high-energy collision between two nuclei is the opposite process of nuclear fission Nuclear fission One nucleus usually undergoes radioactive decay and splits into two smaller nuclei. Using high-energy subatomic particles or photons to bombard can also change the atomic nucleus. If the number of protons in the nucleus changes in a process, the atom becomes an atom of another element.

For two atomic numbers in iron or nickel For the former atomic nuclei, the nuclear fusion between them is a Exothermic process That is to say, the process releases more energy than the energy that connects them. Because of this, Hydrostatic balance 。

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radioactivity

Each element has one or more isotopes with unstable atomic nuclei, which can cause radioactive decay. In this process, the atomic nuclei can release particles or electromagnetic radiation. When the radius of the atomic nucleus is larger than the radius of the strong force, radioactive decay may occur, while the radius of the strong force is only a few fly meters.

The most common radioactive decay is as follows:

Alpha decay : The nucleus releases an alpha particle, that is, a helium nucleus containing two protons and two neutrons. The result of decay is a Atomic number Lower new elements.
Beta decay The phenomenon of weak interaction, in which a neutron is transformed into a proton or a proton into a neutron. The former is accompanied by an electron and a Antineutrino And the latter releases one positron And a neutrino 。 The electrons or positrons released are called beta particles. Therefore, β decay can increase or decrease the atomic number of the atom by one.
Gamma decay : The energy level of the atomic nucleus decreases, releasing electromagnetic wave radiation, which usually occurs after the release of alpha particles or beta particles.

Half lives of isotopes with Z protons and N neutrons

Other relatively rare radioactive decay also includes the release of neutrons or protons nucleon Group or electron group, via Internal conversion Generate high-speed electrons instead of Beta ray And high-energy photons rather than gamma rays.

Each radioisotope has a characteristic decay period, that is, a half-life. half life It is the time required for half of the sample to decay. This is a kind of Exponential decay That is, the sample decays 50% in each half life. In other words, after two half lives, only 25% of the initial isotope remains.

magnetic moment

Basic particles have an inherent property, just like in macro physics centroid All rotating objects have angular momentum Same as in quantum mechanics Is called spin 。 But strictly speaking, these particles are only points and cannot rotate. The unit of spin is Reduced Planck constant The spins of electrons, protons and neutrons are all ½. In atoms, electrons move around the nucleus, so in addition to spin, they have Orbital angular momentum 。 For the atomic nucleus, the orbital angular momentum originates from its own spin.

Just as a rotating charged object can produce magnetic field Similarly, the magnetic field generated by an atom, that is, its magnetic moment , is It is determined by these different angular momenta. Then, spin should have the greatest effect on it. Because one of the properties of the electron is to conform to Pauli exclusion principle , that is, two cannot be located in the same quantum state So when electrons are paired, one spin is always up and the other spin is down. In this way, the magnetic fields generated by them cancel each other out. For some atoms with even number of electrons, the total magnetic dipole moment will be reduced to zero.

about Ferromagnetism The element of, for example, iron, will produce a net magnetic moment because the total number of electrons is odd. At the same time, due to the overlap of adjacent atomic orbits and other reasons, when the unpaired electrons all face the same direction, the total energy of the system is the lowest. This process is called Exchange interaction 。 When the magnetic momentum of these ferromagnetic elements is uniformly backward, the whole material will have a macroscopic measurable magnetic field. Paramagnetism In materials, the atomic magnetic moments are randomly distributed without external magnetic field; After the external magnetic field is applied, all atoms will face uniformly to generate a magnetic field.

The nucleus can also have a net spin. because heat balance Usually these nuclei are randomly oriented. But for some specific elements, such as xenon -129, part of the nuclear spin may also be polarization This state is called Hyperpolarization , on Magnetic resonance imaging It has very important applications.

energy level

In atoms, electronic potential energy It is inversely proportional to its distance from the nucleus. Measure the potential energy of an electron. The usual measurement is the energy required to separate the electron from the atom. The unit is Electron volt （eV）。 In the quantum mechanical model, electrons can only occupy a group of states centered on the atomic nucleus, and each state corresponds to an energy level. The lowest level is called the ground state, and the higher level is called the excited state.

The premise for an electron to transition between two energy levels is that it must absorb or release energy, which must also be consistent with the energy difference between the two energy levels. Because released light The energy of the photon is only related to the frequency of the photon, and the energy level is discontinuous Electromagnetic spectrum There will be some discontinuous bands. Each element has a characteristic spectrum, which depends on the number of nuclear charges, the filling of electrons, the electromagnetic interaction between electrons and some other factors.

An example of absorption lines: the Franc and Fiat lines of the sun

When a beam of full spectrum light passes through a cloud of gas or plasma, some photons will be absorbed by atoms, making the electrons in these atoms transition. The electrons in the excited state will spontaneously return to the low-energy state, and the energy difference will be released to a random direction as photons. The former gives those atoms a filter like function, and the observer will find some black Absorption band 。 The latter can make observers who are not in the same line with light observe some discontinuous spectral lines, which are actually those of atoms Emission line 。 The composition and physical properties of the substance can be known by spectroscopic measurement of these spectral lines.

After careful analysis of spectral lines, scientists found that some spectral lines have fine structure Of Fission 。 This is because of the interaction between spin and the motion of the outermost electron, also known as Spin orbit coupling 。 When an atom is in an external magnetic field, the spectral line can be split into three or more parts. This phenomenon is called Zeeman effect The reason is the atomic magnetic moment and the interaction between the electron and the external magnetic field. Some atoms have many electrons of the same energy level, so only one spectral line is generated. When these atoms are placed outside magnetic field In the middle, there are some small differences in the energy levels of these electron arrangements, which leads to splitting. The existence of an external electric field can also lead to a similar phenomenon, which is called Stark effect 。

If an electron is in the excited state, a photon with appropriate energy can make the electron Stimulated radiation , releasing a photon with the same energy. The premise is that the energy released by the electron returning to the low energy level must be consistent with the energy of the photon acting on it. At this time, the stimulated photon and the original photon move in the same direction, that is, the waves of the two photons are synchronized. Using this principle, people have designed laser , used to produce a beam with a very narrow frequency coherent Light source.

state

Bose Einstein condensate

There are many different substances Phase state There are atoms in it, and these phase states are determined by certain physical conditions, such as temperature and pressure 。 By changing these conditions, the substance can Plasma Conversion between. In the same phase state, substances can also have different forms, for example, solid carbon has two forms of graphite and diamond.

When the temperature is very close Absolute zero Atoms can form Bose Einstein condensate 。 These ultracold atoms can be regarded as Superatomic , enabling scientists to study quantum mechanics Some basic principles of.

Important parameters

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Mass number

(mass number) Since the mass of protons and neutrons is similar and far greater than that of electrons, the relative atomic mass is defined by the sum of the number of protons and neutrons of atoms, which is called the mass number.

Relative atomic mass

The static mass of an atom is usually unified Atomic mass unit (u) Is also called Dalton （Da）。 This unit is defined as one twelfth of the mass of electrically neutral carbon 12, about 1.66 × 10 ⁻ ² ⁷ kg. The lightest hydrogen isotope Protium is the lightest atom with a weight of about 1.007825u. The mass of an atom is approximately the product of the mass number and the atomic mass unit. The heaviest stable atom is lead - 208, with a mass of 207.9766521u.

Mole

Even the heaviest atoms are difficult for chemists to operate on directly, so they usually use another unit mole. The definition of mole is that for any element, a mole always contains the same number of atoms, about 6.022 × 10 ² ³ [2010 CODATA data:

】。 Therefore, if the atomic mass of an element is 1 u, the atomic mass of one mole is (1.66 × 10 ⁻ ² ⁷ x6.022 × 10 ² ³ =9.99652x10⁻⁴≈10x10⁻⁴=0.001kg） 0.001 kg, that is, 1 g. For example, the atomic mass of carbon-12 is 12u, and the mass of a mole of carbon is 0.012kg.

Atomic substance

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Metal elements (e.g. iron, copper, aluminum, etc.)

A few non-metallic simple substances (e.g. diamond, graphite, phosphorus, etc.)

Rare gas (e.g. helium, neon, argon)

The difference between atoms and ions

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		atom	Ions
		atom	cation	anion
area other	structure	The number of protons equals the number of extranuclear electrons	The number of protons is greater than the number of extranuclear electrons	The number of protons is less than the number of extranuclear electrons
	Electrical property	Imperceptibility	With positive charge	negative electrification
	Symbol	Element symbol	Ion symbol (H+)	Ionic symbol (Cl ⁻)

Origin and current situation

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Nucleosynthesis

Stable protons and electrons big bang Appears within one second after. In the next three minutes, Primordial nucleosynthesis Produced most of the helium 、 lithium and deuterium , it may also produce some beryllium and boron 。 In theory, the first atoms (bound electrons) were generated about 380000 years after the Big Bang. This era is called Recombine By this time, the universe had cooled enough to combine electrons with the nucleus. Since then, the nucleus has been fixed star Passed in nuclear fusion The process of combining, producing elements up to iron.

Isotopes like lithium-6 pass through Cosmic ray spallation Generated. This phenomenon occurs when high-energy protons collide with atomic nuclei, resulting in a large number of nucleons being ejected. Elements heavier than iron Supernova Passed in r-process Generated, or at AGB star Passed in S-process In both processes, neutrons are captured by atomic nuclei. Elements like lead mostly pass through heavier elements Nuclear decay Generated.

earth

Most of the atoms that make up the earth and its inhabitants have existed since the formation of the solar system. Some atoms are the result of nuclear decay, and their relative proportions can be used to Radiometric dating decision Age of the Earth 。 Most of the earth's crust helium Both Alpha decay The product of.

There are very few atoms on the earth that did not exist at the beginning, nor were they the result of radioactive decay. Carbon-14 It is produced by cosmic rays in the atmosphere. Some of the earth's atoms are the products of nuclear reactors or nuclear explosions, either deliberately made or as by-products. At all Transuranic element -- Of the elements with atomic number greater than 92, only plutonium And neptunium occur naturally on earth. The life of transuranic elements is shorter than the age of the earth, so many of these elements have already decayed, with only trace amounts Plutonium-244 Exceptions. The natural deposits of plutonium and neptunium are formed by Neutron capture Generated.

The earth contains about 1.33x10E50 atoms. In the earth's atmosphere, there is a small amount of inert gas Atoms, such as argon and neon 。 The remaining 99% of the atmosphere is bound in the form of molecules, including carbon dioxide 、 Diatomic Of oxygen and nitrogen 。 On the surface of the earth, atoms combine and form various compounds, including water , salt silicate and oxide 。 Atoms can also be combined to form substances without independent molecules, including crystals and liquid or solid metals.

Rare and theoretical form

Although elements with atomic number greater than 82 (lead) are known to be radioactive, for elements with atomic number greater than 103“ Stable island ”The concept of. In these Superheavy element One nucleus may be relatively stable than the other. The most likely stable superheavy element is Ubh It has 126 protons and 184 neutrons.

Each particle has a corresponding Antimatter Particles have opposite charges. Therefore, positron It is an antielectron with positive charge, and an antiproton is a particle equivalent to the proton but with negative charge. For unknown reasons, antimatter is very rare in the universe, so no anti atom is found in nature. However, in 1996 Geneva Of European Centre for Nuclear Research , first synthesized antihydrogen -- Antimatter of hydrogen.

Substitution of protons, neutrons or electrons in atoms with other particles of equal charge can form Exotic atom 。 For example, we can use higher quality Muon Substitute muonic atom 。 These types of atoms can be used to test the basic predictions of physics.

Atomic radius

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Atoms have no precise definition Outermost layer The atomic radius is usually measured according to the average nuclear distance between adjacent atoms.

Covalent radius

We measured chlorine Of two Cl atoms in the molecule Nuclear spacing If it is 1.988 α, half of the nuclear spacing, i.e. 0.994 α, is defined as the radius of the chlorine atom, which is called the covalent radius. The covalent radius is the single substance of the element Key length Half of.

Metal radius

In addition, we can also measure Metal element For example, half of the nuclear distance between two adjacent copper atoms in copper is called the metal radius^[15] 。

Vander Waals radius

It refers to that in the molecular crystal Van der Waals A combination, such as a rare gas, that is half the distance between two adjacent nuclei.

The following table shows the atomic radius of some elements（ pm ）, data from Inorganic Chemistry Fourth Edition (2000^[17] ）And j.chem.phys （1967）。

Atomic radius table of some elements
element	hydrogen	helium	lithium	beryllium	boron	carbon	nitrogen	oxygen	fluorine	neon
radius	thirty-seven	one hundred and twenty-two	one hundred and fifty-two	one hundred and eleven	eighty-eight	seventy-seven	seventy	sixty-six	sixty-four	one hundred and sixty
element	sodium	magnesium	aluminum	silicon	phosphorus	sulfur	chlorine	argon	potassium	calcium
radius	one hundred and eighty-six	one hundred and sixty	one hundred and forty-three	one hundred and seventeen	one hundred and ten	one hundred and four	ninety-nine	one hundred and ninety-one	two hundred and twenty-seven	one hundred and ninety-seven
element	scandium	titanium	vanadium	chromium	manganese	iron	cobalt	nickel	copper	zinc
radius	one hundred and sixty-one	one hundred and forty-five	one hundred and thirty-two	one hundred and twenty-five	one hundred and twenty-four	one hundred and twenty-four	one hundred and twenty-five	one hundred and twenty-five	one hundred and twenty-eight	one hundred and thirty-three
element	gallium	germanium	arsenic	selenium	bromine	krypton	rubidium	strontium	yttrium	zirconium
radius	one hundred and twenty-two	one hundred and twenty-two	one hundred and twenty-one	one hundred and seventeen	one hundred and fourteen	one hundred and ninety-eight	two hundred and forty-eight	two hundred and fifteen	one hundred and eighty-one	one hundred and sixty
element	niobium	molybdenum	Technetium	ruthenium	rhodium	palladium	silver	cadmium	indium	tin
radius	one hundred and forty-three	one hundred and thirty-six	one hundred and thirty-six	one hundred and thirty-three	one hundred and thirty-five	one hundred and thirty-eight	one hundred and forty-four	one hundred and forty-nine	one hundred and sixty-three	one hundred and forty-one
element	antimony	tellurium	iodine	xenon	cesium	barium
radius	one hundred and forty-one	one hundred and thirty-seven	one hundred and thirty-three	two hundred and seventeen	two hundred and sixty-five	two hundred and seventeen

Note: In the table Nonmetallic element Is the covalent radius, the metal element is the metal radius, and the rare gas is the van der Waals radius

Note: The radius values of many elements vary greatly in different books for the following reasons:

① The unit of atomic radius is (pm) and angstrom (α), α=100pm.

② The atomic radius is measured in different ways.

③ There are different kinds of atomic radii.

Periodic law of atomic radius

In the periodic table of elements, the general trend of atomic radius change is to increase from top to bottom and decrease from left to right. So the smallest atom is hydrogen , the radius is 0.28 α; The largest atom is cesium , the radius is 2.655 α. Because such dimensions are far smaller than the wavelength of visible light (about 400~700nm), they cannot be observed through an optical microscope. However, using a scanning tunneling microscope, we can observe individual atoms.

magnetic

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summary

The electron is a Charged body , just like all charged bodies, when the electron rotates, a magnetic field Therefore, different atoms often have different magnetic properties.

Molecular orbital theory can well explain the magnetic problems of molecules, such as oxygen Paramagnetism of^[13] 。

Diamagnetism

In the atoms of some substances Electron magnetic moment They cancel each other and the magnetic moment is zero. When subjected to an external magnetic field, the movement of the electron orbit will change, and a small magnetic moment will be generated in the opposite direction to the external magnetic field. Common diamagnetic metals are Bi, Cu, Ag and Au.

Paramagnetism

The main feature of paramagnetic materials is that atoms or molecules contain electronic magnetic moments that are not completely offset, so they have atomic or molecular magnetic moments. however Atomic magnetic moment There is no strong interaction between them (generally Exchange action ）Therefore, the atomic magnetic moments are in a random (chaotic) arrangement under the influence of thermal turbulence, and the atomic magnetic moments cancel each other without magnetic moment. However, when subjected to the external magnetic field, these atomic magnetic moments that were originally disorderly arranged under the thermal turbulence are simultaneously subjected to the magnetic field to make them tend to the magnetic field arrangement and the thermal turbulence action to make them tend to disorderly arrangement. Therefore, the overall effect is that there is a certain magnetic moment component in the direction of the external magnetic field. This makes Magnetic susceptibility (The ratio of magnetization to magnetic field intensity) becomes positive, but the value is also very small. Generally, the susceptibility of paramagnetic materials is about one hundred thousandth (10 ⁻⁻), and increases with the decrease of temperature.

Common paramagnetic substances include oxygen nitric oxide , platinum.

Nuclear property

radioactivity

Of certain substances Nucleus It can decay and emit rays that can neither be seen nor felt by the naked eye, and can only be detected by special instruments radial 。 This property of matter is called radioactivity.

decay

Unstable (i.e. radioactive) nuclei are emitting particle And energy can become more stable, this process is called decay（ Radioactive decay ）。 These particles or energies (the latter electromagnetic wave Mode emission) collectively referred to as radiation（ radiation ）。 The radiation emitted from unstable atomic nuclei can be alpha (helium atomic nuclei) particles, beta (electrons or positrons) particles, gamma rays or neutrons.

During the decay of radionuclides nuclide The number of nuclei will gradually decrease. The time required to decay to only half of the original mass is called the half life （ half-life ）。 Each radionuclide has its specific half-life, which consists of Microsecond To millions of years.

The phenomenon that an atomic nucleus becomes a new nucleus because it emits certain particles. The atomic nucleus is a quantum system, Nuclear decay It is the spontaneous change of atomic nucleus, which is a quantum transition Process, which obeys quantum Statistical law For any radionuclide, the exact time of its decay is unpredictable, but as a whole, the law of decay is very clear. If the number of nuclear decay in the dt time interval is dN, it must be proportional to the number of atomic nuclei that exist at that time N, and obviously also proportional to the time interval dt.

There are three kinds of decay: alpha decay, beta decay and gamma decay.

Nuclear fission （ nuclear fission ）

Nuclear fission refers to the change of one atomic nucleus splitting into several atomic nuclei. Nuclear fission is usually caused by neutrons bombarding atomic nuclei with large masses, Nuclear fission Then two parts with the same mass will be formed and energy will be released, sometimes leading to chain reaction Occurrence of. Energy=mass X light speed Square of^[18]

nuclear fusion

Nuclear fusion is a form of nuclear reaction in which small atoms, mainly deuterium or tritium, polymerize with each other under certain conditions (such as ultra-high temperature and high pressure) to generate new heavier nuclei accompanied by huge energy release. There is huge energy in the atomic nucleus. The change of atomic nucleus (from one atomic nucleus to another) is often accompanied by the release of energy.

If it changes from a heavy nucleus to a light nucleus, it is called nuclear fission, such as an atomic bomb explosion; If a light nucleus changes into a heavy one, it is called nuclear fusion, such as the sun and the hydrogen bomb. Now mankind can only make peaceful use of nuclear fission, not peaceful use of nuclear fusion.

stability

The stability of the atomic nucleus means that the atomic nucleus will not spontaneously change its proton number, neutron number and its basic properties. According to the stability of atomic nuclei, they can be divided into stable atomic nuclei and unstable (or radioactive) atomic nuclei.

1. The nucleus with the proton number equal to or greater than 84 is unstable. That is, elements after atomic number 84 are radioactive elements.

2. The nucleus of an atom with less than 84 protons is stable when the number of protons and neutrons is even.

3. Nuclei with proton number or neutron number equal to 2, 8, 20, 28, 50, 82126 are particularly stable. These numbers are called magic numbers. The number of protons and neutrons are magic numbers, called double magic nuclei.

4. The ratio of neutron number to proton number n/p, when Z<20, n/p=1, the nucleus is stable. With the increase of atomic number, the n/p value increases, and the greater the ratio, the worse the stability.

nuclear decay

An unstable atomic nucleus will spontaneously transform into another nucleus and emit radiation at the same time. This change is called radioactive decay. There are three kinds of rays emitted by atomic nuclei in the process of decay: alpha rays, beta rays and gamma rays

Alpha rays are alpha particle streams, which are positively charged helium nuclei. Beta ray is a stream of electrons moving at high speed.

There are two types of beta decay: beta+and beta -. When beta decays, it emits not only positrons or negative electrons, but also neutrinos or anti neutrinos. Beta decay refers to the transformation of neutrons into protons (staying in the nucleus) in the atomic nucleus and the release of an electron and the anti neutrino associated with the electron. Beta+decay means that the number of neutrons in the atomic nucleus is small, the proton is converted into neutrons (left in the nucleus), and a positron and a neutrino are released at the same time.

Gamma rays are photon streams. It is usually radiated when a new nucleus is formed after alpha decay or beta decay. This is because the radioactive parent nucleus becomes a daughter nucleus in the excited state after the above decay. When the daughter nucleus transitions to the normal state, it generally emits gamma photons.

The total charge and mass of particles before decay are equal to the total charge and mass of all particles after decay

radioactivity Law of decay

There are N nuclei in the sample at time t, and dN nuclei decay in dt time

t=0，N=N0， yes

The above equation is called radioactive decay law.

Physical meaning: at time t, the ratio of the number of atomic nuclei decayed per unit time to the total number of atomic nuclei at that time. The larger, the faster the decay.

It is customary to use half-life to characterize the decay rate of radioactive elements. The half-life is defined as the time required for the nuclear decay to N=N0/2. It is represented by T.

Sometimes, the average life τ is used to indicate the decay rate. The average life is the average of the time that exists before the decay of each atomic nucleus.

Radioactivity (also known as radioactive intensity) refers to the number of nuclear decays of a radioactive source in a unit time.

In the International System of Units, the unit of radioactivity is Becquerel (Bq). 1Bq represents the activity of the radioactive source that undergoes one nuclear decay per second. The common unit is the Curie (Ci).

spectrum

Main entry: Atomic orbital

In a stable state, the electrons in the atom are in the orbit closest to the nucleus, and the atom is called Ground state atom ； The electron absorbs energy and transitions to a higher orbit, when the atom is in excited state 。 Because the atomic orbit is quantized, when the atomic energy changes, it will absorb (release) specific energy and produce different spectral images, Gustav Robert Kirhoff （ Gustav Robert Kirchhoff ）And Robert Wilhelm Bunsen （ Robert Wilhelm Bunson ）This property was first used to identify atoms of different elements.

Flame reaction （ flame test ）

When the atomic spectrum falls in the visible light area, the naked eye can see different colors, which is caused by the burning of some elements' atoms flame The reason for color change, which is called flame reaction, can roughly detect the existence of some element atoms.

The following table shows the colors produced by the flame reaction of some metals (or metal ions):

category	lithium Ions	Sodium ion	Potassium ion	rubidium Ions	calcium ion	strontium Ions	Barium ion	Copper ion
colour	Purplish red	yellow	Lilac	purple	Brick red	Magenta	Yellow green	green

valence electron

valence electron Is the number of electrons, valence electrons and atomic chemical property Closely related, for the main group elements, the number of valence electrons is equal to its Number of outermost electrons ； about Subfamily elements The number of valence electrons includes the number of outermost electrons and the number of d (and sometimes f) orbitals in the secondary outer layer Electronic layout Identify the valence electrons of a particular element. According to the different valence electrons, the periodic table of elements can be divided into s area, p area, d area, ds area and f area^[13] 。

Valence

ionization energy

ionization energy The size of reflects how easy it is for atoms to lose electrons. The smaller the ionization energy, the easier it is for atoms to lose electrons, and vice versa; The size of ionization energy is closely related to the effective charge of atoms, atomic radius and electron arrangement.

First ionization energy

The energy required for the ground state gas atom to lose electrons and become a positive charged gas cation is called the first ionization energy. Generally speaking, if not stated, the ionization energy is the first ionization energy.

1st～10th

The following are the first to tenth ionization energies of all the elements found. The data source is unknown. Unit: kJ/mol (kJ/mol)

	1st	2nd	3rd	4th	5th	6th	7th	8th	9th	10th
hydrogen	one thousand three hundred and twelve
helium	two thousand three hundred and seventy-two point three	five thousand two hundred and fifty point five
lithium	five hundred and twenty point two	seven thousand two hundred and ninety-eight point one	eleven thousand eight hundred and fifteen
beryllium	eight hundred and ninety-nine point five	one thousand seven hundred and fifty-seven point one	fourteen thousand eight hundred and forty-eight point seven	twenty-one thousand and six point six
boron	eight hundred point six	two thousand four hundred and twenty-seven point one	three thousand six hundred and fifty-nine point seven	twenty-five thousand and twenty-five point eight	thirty-two thousand eight hundred and twenty-six point seven
carbon	one thousand and eighty-six point five	two thousand three hundred and fifty-two point six	four thousand six hundred and twenty point five	six thousand two hundred and twenty-two point seven	thirty-seven thousand eight hundred and thirty-one	forty-seven thousand two hundred and seventy-seven
nitrogen	one thousand four hundred and two point three	two thousand eight hundred and fifty-six	four thousand five hundred and seventy-eight point one	seven thousand four hundred and seventy-five	nine thousand four hundred and forty-four point nine	fifty-three thousand two hundred and sixty-six point six	sixty-four thousand three hundred and sixty
oxygen	one thousand three hundred and thirteen point nine	three thousand three hundred and eighty-eight point three	five thousand and three hundred point five	seven thousand four hundred and sixty-nine point two	ten thousand nine hundred and eighty-nine point five	thirteen thousand three hundred and twenty-six point five	seventy-one thousand three hundred and thirty	eighty-four thousand and seventy-eight
fluorine	one thousand six hundred and eighty-one	three thousand three hundred and seventy-four point two	six thousand and fifty point four	eight thousand four hundred and seven point seven	eleven thousand and twenty-two point seven	fifteen thousand one hundred and sixty-four point one	seventeen thousand eight hundred and sixty-eight	ninety-two thousand and thirty-eight point one	one hundred and six thousand four hundred and thirty-four point three
neon	two thousand and eighty point seven	three thousand nine hundred and fifty-two point three	six thousand one hundred and twenty-two	nine thousand three hundred and seventy-one	twelve thousand one hundred and seventy-seven	fifteen thousand two hundred and thirty-eight	nineteen thousand nine hundred and ninety-nine	twenty-three thousand and sixty-nine point five	one hundred and fifteen thousand three hundred and seventy-nine point five	one hundred and thirty-one thousand four hundred and thirty-two
sodium	four hundred and ninety-five point eight	four thousand five hundred and sixty-two	six thousand nine hundred and ten point three	nine thousand five hundred and forty-three	thirteen thousand three hundred and fifty-four	sixteen thousand six hundred and thirteen	twenty thousand one hundred and seventeen	twenty-five thousand four hundred and ninety-six	twenty-eight thousand nine hundred and thirty-two	one hundred and forty-one thousand three hundred and sixty-two
magnesium	seven hundred and thirty-seven point seven	one thousand four hundred and fifty point seven	seven thousand seven hundred and thirty-two point seven	ten thousand five hundred and forty-two point five	thirteen thousand six hundred and thirty	eighteen thousand and twenty	twenty-one thousand seven hundred and eleven	twenty-five thousand six hundred and sixty-one	thirty-one thousand six hundred and fifty-three	thirty-five thousand four hundred and fifty-eight
aluminum	five hundred and seventy-seven point five	one thousand eight hundred and sixteen point seven	two thousand seven hundred and forty-four point eight	eleven thousand five hundred and seventy-seven	fourteen thousand eight hundred and forty-two	eighteen thousand three hundred and seventy-nine	twenty-three thousand three hundred and twenty-six	twenty-seven thousand four hundred and sixty-five	thirty-one thousand eight hundred and fifty-three	thirty-eight thousand four hundred and seventy-three
silicon	seven hundred and eighty-six point five	one thousand five hundred and seventy-seven point one	three thousand two hundred and thirty-one point six	four thousand three hundred and fifty-five point five	sixteen thousand and ninety-one	nineteen thousand eight hundred and five	twenty-three thousand seven hundred and eighty	twenty-nine thousand two hundred and eighty-seven	thirty-three thousand eight hundred and seventy-eight	thirty-eight thousand seven hundred and twenty-six
phosphorus	one thousand and eleven point eight	one thousand nine hundred and seven	two thousand nine hundred and fourteen point one	four thousand nine hundred and sixty-three point six	six thousand two hundred and seventy-three point nine	twenty-one thousand two hundred and sixty-seven	twenty-five thousand four hundred and thirty-one	twenty-nine thousand eight hundred and seventy-two	thirty-five thousand nine hundred and five	forty thousand nine hundred and fifty
sulfur	nine hundred and ninety-nine point six	two thousand two hundred and fifty-two	three thousand three hundred and fifty-seven	four thousand five hundred and fifty-six	seven thousand and four point three	eight thousand four hundred and ninety-five point eight	twenty-seven thousand one hundred and seven	thirty-one thousand seven hundred and nineteen	thirty-six thousand six hundred and twenty-one	forty-three thousand one hundred and seventy-seven
chlorine	one thousand two hundred and fifty-one point two	two thousand two hundred and ninety-eight	three thousand eight hundred and twenty-two	five thousand one hundred and fifty-eight point six	six thousand five hundred and forty-two	nine thousand three hundred and sixty-two	eleven thousand and eighteen	thirty-three thousand six hundred and four	thirty-eight thousand and six hundred	forty-three thousand nine hundred and sixty-one
argon	one thousand five hundred and twenty point six	two thousand six hundred and sixty-five point eight	three thousand nine hundred and thirty-one	five thousand seven hundred and seventy-one	seven thousand two hundred and thirty-eight	eight thousand seven hundred and eighty-one	eleven thousand nine hundred and ninety-five	thirteen thousand eight hundred and forty-two	forty thousand seven hundred and sixty	forty-six thousand one hundred and eighty-six
potassium	four hundred and eighteen point eight	three thousand and fifty-two	four thousand four hundred and twenty	five thousand eight hundred and seventy-seven	seven thousand nine hundred and seventy-five	nine thousand five hundred and ninety	eleven thousand three hundred and forty-three	fourteen thousand nine hundred and forty-four	sixteen thousand nine hundred and sixty-three point seven	forty-eight thousand six hundred and ten
calcium	five hundred and eighty-nine point eight	one thousand one hundred and forty-five point four	four thousand nine hundred and twelve point four	six thousand four hundred and ninety-one	eight thousand one hundred and fifty-three	ten thousand four hundred and ninety-six	twelve thousand two hundred and seventy	fourteen thousand two hundred and six	eighteen thousand one hundred and ninety-one	twenty thousand three hundred and eighty-five
scandium	six hundred and thirty-three point one	one thousand two hundred and thirty-five	two thousand three hundred and eighty-eight point six	seven thousand and ninety point six	eight thousand eight hundred and forty-three	ten thousand six hundred and seventy-nine	thirteen thousand three hundred and ten	fifteen thousand two hundred and fifty	seventeen thousand three hundred and seventy	twenty-one thousand seven hundred and twenty-six
titanium	six hundred and fifty-eight point eight	one thousand three hundred and nine point eight	two thousand six hundred and fifty-two point five	four thousand one hundred and seventy-four point six	nine thousand five hundred and eighty-one	eleven thousand five hundred and thirty-three	thirteen thousand five hundred and ninety	sixteen thousand four hundred and forty	eighteen thousand five hundred and thirty	twenty thousand eight hundred and thirty-three
vanadium	six hundred and fifty point nine	one thousand four hundred and fourteen	two thousand eight hundred and thirty	four thousand five hundred and seven	six thousand two hundred and ninety-eight point seven	twelve thousand three hundred and sixty-three	fourteen thousand five hundred and thirty	sixteen thousand seven hundred and thirty	nineteen thousand eight hundred and sixty	twenty-two thousand two hundred and forty
chromium	six hundred and fifty-two point nine	one thousand five hundred and ninety point six	two thousand nine hundred and eighty-seven	four thousand seven hundred and forty-three	six thousand seven hundred and two	eight thousand seven hundred and forty-four point nine	fifteen thousand four hundred and fifty-five	seventeen thousand eight hundred and twenty	twenty thousand one hundred and ninety	twenty-three thousand five hundred and eighty
manganese	seven hundred and seventeen point three	one thousand five hundred and nine	three thousand two hundred and forty-eight	four thousand nine hundred and forty	six thousand nine hundred and ninety	nine thousand two hundred and twenty	eleven thousand and five hundred	eighteen thousand seven hundred and seventy	twenty-one thousand and four hundred	twenty-three thousand nine hundred and sixty
iron	seven hundred and sixty-two point five	one thousand five hundred and sixty-one point nine	two thousand nine hundred and fifty-seven	five thousand two hundred and ninety	seven thousand two hundred and forty	nine thousand five hundred and sixty	twelve thousand and sixty	fourteen thousand five hundred and eighty	twenty-two thousand five hundred and forty	twenty-five thousand two hundred and ninety
cobalt	seven hundred and sixty point four	one thousand six hundred and forty-eight	three thousand two hundred and thirty-two	four thousand nine hundred and fifty	seven thousand six hundred and seventy	nine thousand eight hundred and forty	twelve thousand four hundred and forty	fifteen thousand two hundred and thirty	seventeen thousand nine hundred and fifty-nine	twenty-six thousand five hundred and seventy
nickel	seven hundred and thirty-seven point one	one thousand seven hundred and fifty-three	three thousand three hundred and ninety-five	five thousand and three hundred	seven thousand three hundred and thirty-nine	ten thousand and four hundred	twelve thousand and eight hundred	fifteen thousand and six hundred	eighteen thousand and six hundred	twenty-one thousand six hundred and seventy
copper	seven hundred and forty-five point five	one thousand nine hundred and fifty-seven point nine	three thousand five hundred and fifty-five	five thousand five hundred and thirty-six	seven thousand and seven hundred	nine thousand and nine hundred	thirteen thousand and four hundred	sixteen thousand	nineteen thousand and two hundred	twenty-two thousand and four hundred
zinc	nine hundred and six point four	one thousand seven hundred and thirty-three point three	three thousand eight hundred and thirty-three	five thousand seven hundred and thirty-one	seven thousand nine hundred and seventy	ten thousand and four hundred	twelve thousand and nine hundred	sixteen thousand and eight hundred	nineteen thousand and six hundred	twenty-three thousand
gallium	five hundred and seventy-eight point eight	one thousand nine hundred and seventy-nine point three	two thousand nine hundred and sixty-three	six thousand one hundred and eighty
germanium	seven hundred and sixty-two	one thousand five hundred and thirty-seven point five	three thousand three hundred and two point one	four thousand four hundred and eleven	nine thousand and twenty
arsenic	nine hundred and forty-seven	one thousand seven hundred and ninety-eight	two thousand seven hundred and thirty-five	four thousand eight hundred and thirty-seven	six thousand and forty-three	twelve thousand three hundred and ten
selenium	nine hundred and forty-one	two thousand and forty-five	two thousand nine hundred and seventy-three point seven	four thousand one hundred and forty-four	six thousand five hundred and ninety	seven thousand eight hundred and eighty	fourteen thousand nine hundred and ninety
bromine	one thousand one hundred and thirty-nine point nine	two thousand one hundred and three	three thousand four hundred and seventy	four thousand five hundred and sixty	five thousand seven hundred and sixty	eight thousand five hundred and fifty	nine thousand nine hundred and forty	eighteen thousand and six hundred
krypton	one thousand three hundred and fifty point eight	two thousand three hundred and fifty point four	three thousand five hundred and sixty-five	five thousand and seventy	six thousand two hundred and forty	seven thousand five hundred and seventy	ten thousand seven hundred and ten	twelve thousand one hundred and thirty-eight	twenty-two thousand two hundred and seventy-four	twenty-five thousand eight hundred and eighty
rubidium	four hundred and three	two thousand six hundred and thirty-three	three thousand eight hundred and sixty	five thousand and eighty	six thousand eight hundred and fifty	eight thousand one hundred and forty	nine thousand five hundred and seventy	thirteen thousand one hundred and twenty	fourteen thousand and five hundred	twenty-six thousand seven hundred and forty
strontium	five hundred and forty-nine point five	one thousand and sixty-four point two	four thousand one hundred and thirty-eight	five thousand and five hundred	six thousand nine hundred and ten	eight thousand seven hundred and sixty	ten thousand two hundred and thirty	eleven thousand and eight hundred	fifteen thousand and six hundred	seventeen thousand and one hundred
yttrium	six hundred	one thousand one hundred and eighty	one thousand nine hundred and eighty	five thousand eight hundred and forty-seven	seven thousand four hundred and thirty	eight thousand nine hundred and seventy	eleven thousand one hundred and ninety	twelve thousand four hundred and fifty	fourteen thousand one hundred and ten	eighteen thousand and four hundred
zirconium	six hundred and forty point one	one thousand two hundred and seventy	two thousand two hundred and eighteen	three thousand three hundred and thirteen	seven thousand seven hundred and fifty-two	nine thousand and five hundred
niobium	six hundred and fifty-two point one	one thousand three hundred and eighty	two thousand four hundred and sixteen	three thousand and seven hundred	four thousand eight hundred and seventy-seven	nine thousand eight hundred and forty-seven	twelve thousand and one hundred
molybdenum	six hundred and eighty-four point three	one thousand five hundred and sixty	two thousand six hundred and eighteen	four thousand four hundred and eighty	five thousand two hundred and fifty-seven	six thousand six hundred and forty point eight	twelve thousand one hundred and twenty-five	thirteen thousand eight hundred and sixty	fifteen thousand eight hundred and thirty-five	seventeen thousand nine hundred and eighty
Technetium	seven hundred and two	one thousand four hundred and seventy	two thousand eight hundred and fifty
ruthenium	seven hundred and ten point two	one thousand six hundred and twenty	two thousand seven hundred and forty-seven
Lawrencium	seven hundred and nineteen point seven	one thousand seven hundred and forty	two thousand nine hundred and ninety-seven
palladium	eight hundred and four point four	one thousand eight hundred and seventy	three thousand one hundred and seventy-seven
silver	seven hundred and thirty-one	two thousand and seventy	three thousand three hundred and sixty-one
cadmium	eight hundred and sixty-seven point eight	one thousand six hundred and thirty-one point four	three thousand six hundred and sixteen
indium	five hundred and fifty-eight point three	one thousand eight hundred and twenty point seven	two thousand seven hundred and four	five thousand two hundred and ten
tin	seven hundred and eight point six	one thousand four hundred and eleven point eight	two thousand nine hundred and forty-three	three thousand nine hundred and thirty point three	seven thousand four hundred and fifty-six
antimony	eight hundred and thirty-four	one thousand five hundred and ninety-four point nine	two thousand four hundred and forty	four thousand two hundred and sixty	five thousand and four hundred	ten thousand and four hundred
tellurium	eight hundred and sixty-nine point three	one thousand seven hundred and ninety	two thousand six hundred and ninety-eight	three thousand six hundred and ten	five thousand six hundred and sixty-eight	six thousand eight hundred and twenty	thirteen thousand and two hundred
iodine	one thousand and eight point four	one thousand eight hundred and forty-five point nine	three thousand one hundred and eighty
xenon	one thousand one hundred and seventy point four	two thousand and forty-six point four	three thousand and ninety-nine point four
cesium	three hundred and seventy-five point seven	two thousand two hundred and thirty-four point three	three thousand and four hundred
barium	five hundred and two point nine	nine hundred and sixty-five point two	three thousand and six hundred
lanthanum	five hundred and thirty-eight point one	one thousand and sixty-seven	one thousand eight hundred and fifty point three	four thousand eight hundred and nineteen	five thousand nine hundred and forty
cerium	five hundred and thirty-four point four	one thousand and fifty	one thousand nine hundred and forty-nine	three thousand five hundred and forty-seven	six thousand three hundred and twenty-five	seven thousand four hundred and ninety
praseodymium	five hundred and twenty-seven	one thousand and twenty	two thousand and eighty-six	three thousand seven hundred and sixty-one	five thousand five hundred and fifty-one
neodymium	five hundred and thirty-three point one	one thousand and forty	two thousand one hundred and thirty	three thousand and nine hundred
Promethium	five hundred and forty	one thousand and fifty	two thousand one hundred and fifty	three thousand nine hundred and seventy
samarium	five hundred and forty-four point five	one thousand and seventy	two thousand two hundred and sixty	three thousand nine hundred and ninety
europium	five hundred and forty-seven point one	one thousand and eighty-five	two thousand four hundred and four	four thousand one hundred and twenty
Rolling	five hundred and ninety-three point four	one thousand one hundred and seventy	one thousand nine hundred and ninety	four thousand two hundred and fifty
terbium	five hundred and sixty-five point eight	one thousand one hundred and ten	two thousand one hundred and fourteen	three thousand eight hundred and thirty-nine
dysprosium	five hundred and seventy-three	one thousand one hundred and thirty	two thousand and two hundred	three thousand nine hundred and ninety
holmium	five hundred and eighty-one	one thousand one hundred and forty	two thousand two hundred and four	four thousand and one hundred
erbium	five hundred and eighty-nine point three	one thousand one hundred and fifty	two thousand one hundred and ninety-four	four thousand one hundred and twenty
Thulium	five hundred and ninety-six point seven	one thousand one hundred and sixty	two thousand two hundred and eighty-five	four thousand one hundred and twenty
Ytterbium	six hundred and three point four	one thousand one hundred and seventy-four point eight	two thousand four hundred and seventeen	four thousand two hundred and three
Lutetium	five hundred and twenty-three point five	one thousand three hundred and forty	two thousand and twenty-two point three	four thousand three hundred and seventy	six thousand four hundred and forty-five
hafnium	six hundred and fifty-eight point five	one thousand four hundred and forty	two thousand two hundred and fifty	three thousand two hundred and sixteen
tantalum	seven hundred and sixty-one	one thousand and five hundred
tungsten	seven hundred and seventy	one thousand and seven hundred
rhenium	seven hundred and sixty	one thousand two hundred and sixty	two thousand five hundred and ten	three thousand six hundred and forty
Osmium	eight hundred and forty	one thousand and six hundred
iridium	eight hundred and eighty	one thousand and six hundred
platinum	eight hundred and seventy	one thousand seven hundred and ninety-one
gold	eight hundred and ninety point one	one thousand nine hundred and eighty
mercury	one thousand and seven point one	one thousand eight hundred and ten	three thousand and three hundred
thallium	five hundred and eighty-nine point four	one thousand nine hundred and seventy-one	two thousand eight hundred and seventy-eight
lead	seven hundred and fifteen point six	one thousand four hundred and fifty point five	three thousand and eighty-one point five	four thousand and eighty-three	six thousand six hundred and forty
bismuth	seven hundred and three	one thousand six hundred and ten	two thousand four hundred and sixty-six	four thousand three hundred and seventy	five thousand and four hundred	eight thousand five hundred and twenty
Polonium	eight hundred and twelve point one
Astatine	nine hundred and ten

electron affinity

first Electron affinity

One ground state gas atom of the element gets an electron to become a univalent gas state anion The energy released when is called the electron affinity energy (Y) of the element. The electron affinity energy of an element represents the energy released when an electron forms a negative ion; If it is negative, it means to absorb energy (it is usually metal with negative affinity energy, and it is difficult to form negative ions).

Electron affinity is an element Oxidizability The greater the electron affinity energy is, the greater the tendency of the atom to acquire electrons is The stronger non-metallic property The regularity of electron affinity is not strong.

Due to the limitation of conditions, there is no accurate method to determine the electron affinity. The electron affinity in different literatures varies greatly and does not show a periodic change rule, so the application of electron affinity is not widespread^[13]^[19] 。

Some are given below Main family elements Electron affinity energy of elements, data from Chemistry - Structure and Properties of Substances (Elective) (2004^[13] ）。

element	hydrogen	lithium	beryllium	boron	carbon	nitrogen	oxygen	fluorine	sodium
Y	seventy-two point eight	fifty-nine point six	－48.6	twenty-six point seven	one hundred and twenty-two	－7	one hundred and forty-one	three hundred and twenty-eight	fifty-two point nine
element	magnesium	aluminum	silicon	phosphorus	sulfur	chlorine	potassium	calcium	gallium
Y	－38.6	forty-two point five	one hundred and thirty-four	seventy-two	two hundred	three hundred and forty-nine	forty-eight point four	－28.9	twenty-eight point nine
element	germanium	arsenic	selenium	bromine	rubidium	strontium	indium	tin	tellurium
Y	one hundred and nineteen	seventy-eight point two	one hundred and ninety-five	three hundred and twenty-five	forty-six point nine	－28.9	twenty-eight point nine	one hundred and seven	one hundred and ninety
element	iodine	cesium	barium	thallium	lead	bismuth	Polonium	Astatine
Y	two hundred and ninety-five	forty-five point five	－28.9	nineteen point three	thirty-five point one	ninety-one point three	one hundred and eighty-three	two hundred and seventy

Second (and above) electron affinity

The second (and above) electron affinity is negative for any element, which is basically meaningless^[19] 。

Electronegativity

Electronegativity It is a group of relative values representing the attraction of atoms to electrons when molecules bond. The electronegativity comprehensively considers the ionization energy and electron affinity energy Linus Carl Pauling （ L.C.Pauling ）It was proposed in 1932. The greater the element electronegativity, the stronger the attraction of atoms to bonding electrons when forming chemical bonds.

computing method

There are many calculation methods of electronegativity, each of which has different electronegativity values, and there are three representative methods.

① Pauling's scale. Based on thermochemical data and molecular Bond energy The electronegativity of fluorine is 3.98, and the relative electronegativity of other elements is calculated.

② Millikan from Ionization potential Absolute electronegativity calculated with the electron affinity energy.

③ The electrons built on the nucleus and bonding atoms proposed by Alai Electrostatic action The electronegativity based on. When using electronegativity value, it must be the same set of values for comparison.

Electronegativity meter

The following table shows the electronegativity of common elements, and the data is taken from Chemistry - Structure and Properties of Substances (Elective) (2004^[13] ）。

element	hydrogen	helium	lithium	beryllium	boron	carbon	nitrogen	oxygen	fluorine
Electronegativity	two point one	－	one	one point five	two	two point five	three	three point five	four
element	neon	sodium	magnesium	aluminum	silicon	phosphorus	sulfur	chlorine	argon

scientific research

Announce

edit

In September 2022, scientists from the United States and Japan will cool ytterbium atoms to one billionth of a degree Celsius above absolute zero in the laboratory, which is the assumed temperature at which all atoms stop moving 。^[21]

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