Valence electron refers toNucleusThe external electron can interact with other atoms to formChemical bondThe electron of is the nucleus followed by the elementValenceRelated electronics.Transitional elementThe valence electron of is not only the outermost electron, but also the second outermost electron and the penultimate third electron of some elements.The valence electrons also determine theconductancePerformance.Generally speaking, the atomicValence electron numberThe less, the higher its activity.
Main family elementsThe valence electron of is the outermost electron of the main group element atom;Transitional elementThe valence electron of is not only the outermost electron, but also the second outermost electron and the penultimate third electron of some elements. For example, sometimes it also includes the D electron of the second outermost layerLanthanide, and the third to last layer of F electrons, which can pass through atomsOrbital energyJudgment: ns ＜ (n-2) f ＜ (n-1) d ＜ np
The valence electrons are atoms participatingchemical reactionThe electrons that can be used for bonding areNucleusAn electron externally related to the valence of an element.stayMain family elementsMedium,Valence electron numbernamelyNumber of outermost electrons。Subfamily elementsIn addition to the outermost electrons, the valence electrons of an atom can also include the secondary outermost electrons.For example,chromiumOfValence electron layerThe structure is 3d54s1, and all six valence electrons can participate in bonding.Lanthanides can also include 4f electrons in the third layer.All valence electrons participate in bonding, and the element shows the highest positiveValence；Some participate in bonding, which has a variety of valence characteristics.For example, the highest valence of chromium is+6, in addition to+5,+4,+3,+2,+1, etc.In the main group of non-metallic elements, except for the second periodic element, there is generally ndEmpty orbit。When these elements followElectronegativityWhen larger elements combine, the valence electrons on the original outermost layer can be disassembled into the nd orbit, and then pass throughTrack hybridizationThese elements have higher chemical valence.
The valence electrons of the outermost shell of an atom dominate the atomicChemical bondeffect.Therefore, atoms with the same valence electron numberperiodic table of ele mentsAre placed in the same column.Generally speaking, the fewer valence electrons of metal atoms, the higher their activity, such asalkali metalThey are very active, including lithium, sodium, potassium, etc. They are the most active group of metals.
Helium atom model
Each atom, if fullvalenceIn other words, the activity will be much lower.There are two ways to achieve this: an atom can share electrons with neighboring atoms to formcovalent bondOr remove electrons from other atoms to formIonic bond。The ionic bond requires one atom to send some of its electrons to another atom, because the entire outer layer can be left with full valence.By moving electrons, two atoms are connected, which is called chemical bond.Chemical bonds cause atoms to form molecules orIonic compound。There are three main chemical bonds and oneSize ratioSlightly less chemically bondedIntermolecular force：
