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Nitrogen group element

Elements of Group V A in the Periodic Table

This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Nitrogen group is located in periodic table of ele ments Ⅴ A element^[3] , including nitrogen （N）、 phosphorus （P）、 arsenic （As）、 antimony （Sb）、 bismuth (Bi) and Fixed (Mc) There are six kinds of elements in this group chemical compound It can present - 3,+1,+2,+3,+4,+5, etc Valence They have five atoms in the outermost layer Electronics 。 The highest normal price is+5.

Chinese name: Nitrogen group element
Foreign name: Nitrogen group

Interpretation: periodic table of ele ments All of family V A element
Total: Six
Foreign alias: pnictogen

catalog

four nitrogen oxide
five chemical reaction

Basic Introduction

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Nitrogen group elements in Crust The mass fractions of nitrogen, phosphorus, arsenic, antimony and bismuth are 0.0025%, 0.1%, 0.000015%, 0.000002% and 0.00000048% respectively.

Nitrogen group element atomic structure The feature is: the outermost part of the atom Electronic layer There are five electrons on the decision They all belong to the fifth A group in the periodic table. Their highest positive price is+5 Gaseous hydride , except that the oxidation number of nitrogen and phosphorus elements is - 3, others are+3, and the chemical formula of gaseous hydride can be RH three express. highest oxide The chemical formula of can be R two O five It indicates that the corresponding hydrate is acid. Most of them are right and wrong metallic element 。^[1]

nature

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Nitrogen group elements Atomic number As the number of electron layers and atomic radius gradually increase, the force of the outermost electrons in the atomic nucleus gradually weakens, and the tendency of atoms to acquire electrons gradually weakens Nonmetallic It also gradually weakens. The obvious performance is their Gaseous hydride The stability gradually weakens (NH ∨>PH ∨>AsH ∨); Their highest price oxide The acidity of corresponding hydrates gradually weakens (HNO three >H three PO four >H three AsO four ）； On the other hand, with Atomic number Increase of, atom loss Electronics The trend of Metallicity Gradually increased, although arsenic is non-metallic, it has shown some metallicity, while antimony and bismuth have obviously shown metallicity.

Nitrogen group elements show a complete transition from typical non-metallic elements to typical metal elements in nature. N and P are non-metallic elements, Sb and Bi are metallic elements, and As in the middle is quasi metallic elements. The valence electron configuration of the elements in this group is ns two 、np three The main oxidation numbers are - 3,+3 and+5. The stability of substances with an oxidation number of+3 from top to bottom increases, while the stability of substances with an oxidation state of+5 decreases. This is because when transiting from top to bottom to bismuth, due to the large radius of bismuth atom, the overlap of electronic clouds is small when bonding, bismuth atoms have 4f and 5d energy levels, while f The shielding effect of the d electron on the atomic nucleus is small, and the 6S electron has a greater penetration effect, so the 6s energy level is significantly reduced, making the 6s electron become an "inert electron pair" and not easy to participate in bonding, and bismuth often shows+3 valence. This phenomenon that the top-down low oxidation state is more stable than the high oxidation state is called the inert electron pair effect.

The bonding feature of the elements in this group is that they are easy to form covalent bonds, which is because they have relatively high ionization energy compared with the front and rear elements in the periodic system. With strong covalence, it is difficult for them to form - 3 ions. Only N and P with large electronegativity can form a few - 3 ionic compounds, but there will be no hydrated ions due to hydrolysis in aqueous solution. It is also very unlikely that the elements of this group can form+3 valence ion, and only the larger radius Sb and Bi can form+3 valence ion compounds. In addition, the elements of this family can not only provide electron pairs as ligands, but also accept the electron pairs of other ligands as central atoms Coordination compound 。^[2]

nitrogen

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physical property

Nitrogen is a colorless and odorless gas with a melting point of 63 K, a boiling point of 77 K, and a critical temperature of 126 K. It is difficult to liquefy. The solubility is very small. A volume of water can dissolve 0.02 volume of nitrogen at 283 K under normal pressure.

preparation

In industry, nitrogen is produced by fractionating liquid air. The saturated solution and solid of heated ammonium chloride are used in the laboratory Sodium nitrite The method of preparing nitrogen with the mixture of.

chemical property

There is a nitrogen nitrogen triple bond in the nitrogen molecule, and the bond energy is very large (941 KJ/mol), so that only 0.1% dissociation occurs when heated to 3273K. The nitrogen molecule is the most stable diatomic molecule known. Nitrogen is the isoelectronic body of CO, which has many similarities in structure and properties.

Different active metals react differently with nitrogen. Direct combination with alkali metal at room temperature; And alkaline-earth metal Generally, it needs to be combined at high temperature; Higher reaction conditions are required for simple substance reactions with other elements.

application

At present, the main way for humans to effectively use nitrogen is to synthesize ammonia, but the requirements are very high. In recent years, people are trying to understand the mechanism of plant nitrogen fixation and try to use chemical methods to simulate Biological nitrogen fixation To realize the development and utilization of nitrogen resources in the air under mild conditions.^[2]

nitrogen oxide

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Type: N ₂ O (commonly known as laughing gas), NO, N ₂ O ₂ (can meet water to generate HNO ₂), NO ₂, N ₂ O4,

N ₂ O5 (generate HNO ∨ when encountering water)^[2]

physical property ： The density of colorless and odorless toxic gas is slightly higher than that of air insoluble in water.

chemical property ： 2NO+O₂=2NO₂

preparation: Laboratory method, 3Cu+8HNO three (dilute)=3Cu (NO three ) two +2NO↑+4H two O^[2]

NO₂

physical property ： The toxic density of reddish brown gas with pungent odor is higher than that of air.

chemical property ： Unstable 2NO ₂ easily turns into N ₂ O4 at room temperature

React with water, 3NO ₂+H ₂ O=2HNO ∨+NO^[2]

chemical reaction

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On nitrogen group elements Chemical equation see below

nitrogen

Nitrogen reacts with metal: 3Mg+N ₂ -- → (ignites) Mg ∨ N ₂

Atmospheric nitrogen fixation: N ₂+O ₂ - → 2NO; 2NO+O₂——→2NO₂ ； 3NO₂+H₂O——→2HNO₃+NO^[1]

ammonia

Synthetic ammonia (artificial nitrogen fixation, industrial ammonia production): N ₂+3H ₂ - high temperature and high pressure, catalyst → 2NH ∨

Laboratory system ammonia ：2NH four Cl + Ca（OH）₂——→CaCl₂+2 NH₃↑+H₂O

ammonia Dissolved in water: NH ∨+H ₂ O -- → NH ∨ · H ₂ O

Ammonia decomposes when heated: NH ∨ · H ₂ O -- → NH ∨ ↑+H ₂ O

Ammonia and hydrochloric acid Reaction of (weakly alkaline): NH ∨+HCl—— → NH four Cl

Ammonia and sulphuric acid Reaction (weakly alkaline): 2NH ≮+H ₂ SO four —— → （NH four ）₂SO four

Ammonia and chlorine Reaction of（ Reducibility ）：8NH₃+3Cl₂—— → 6NH four Cl+N₂

Dry ammonium salt uses alkali lime (mixture of CaO and NaOH) ammonia to react with copper oxide under heating conditions to generate H ₂ O, N ₂, Cu^[1]

ammonium salt

NH four Cl——→NH₃ ↑ + HCl↑