halide

In binary compounds containing halogens, halogens have negative valence

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In halogen containing Binary compound Medium, halogen is negative price The compounds of are called halides. Including fluoride chloride 、 Bromide Iodide and some Halogen intermolecule 。 It can be divided into metal halides and Nonmetal Halides.

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Halogenation matter （halide）

contain fluorine (F) , chlorine (Cl), bromine (Br), iodine (I), astatine (At) halogen elements (halogen for short) are compounds with negative valence. It can be divided into ionic halides and Covalent Type halide. The non-metallic halides such as boron, carbon, silicon, nitrogen, hydrogen, sulfur, and phosphorus are all covalent. Most covalent halides are volatile, with low melting and boiling points. There are three kinds of interactions with water.

(1) Some are easily soluble in water, such as hydrogen halide, ammonium chloride, etc.

(2) Some of them interact with water hydrolysis , such as silicon tetrachloride Phosphorus trichloride , phosphorus pentachloride, etc.

(3) A few are insoluble in water, such as carbon tetrachloride, sulfur hexafluoride, etc. In metal halides alkali metal Most alkaline earth metal halides are Ions Type. It is characterized by high melting and boiling points and is easily soluble in water. Some of other metal halides belong to ionic type, and some belong to covalent bond , no obvious regularity, such as two Ferric chloride It is ionic and ferric chloride is covalent, and there is no absolute limit between them. Halogen intermolecule (e.g Chlorine trifluoride ClF three ）And complex halides (e.g Carnallite KCl·MgCl two ·6H two O)， Broadly speaking, it also belongs to the category of halides.^[1]

Causes

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Halogens are often formed in a variety of geological environments. Some halogens, such as halite, are commonly found in evaporite formation, which is an alternative sedimentary rock stratum, containing evaporite minerals, such as gypsum, halite and Sylvite It is deposited in strict sequence and forms interbedding with marl and limestone. Other halides, such as fluorite, occur in Hydrothermal fluid Lode 。 Halide minerals are usually soft, mostly cubic symmetric crystals, and their specific gravity is small.

Inspection of halides

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Supplies: test tube, test tube rack, test tube clamp, measuring cylinder, alcohol lamp, dropper.

Potassium chloride, potassium bromide, potassium iodide, chlorine water, bromine water, potassium iodide starch solution, silver nitrate, ammonia water.

Principle: most metal halides can be dissolved in polar solvents and ionized into halogen ions. Therefore, they can be tested by the displacement reaction of halogen and the generation of silver salts of different colors. You can also generate hydride The stability is different.

Preparation and operation:

1. Fluoride is tested by reacting fluoride with concentrated sulfuric acid to generate hydrogen fluoride that corrodes glass. See the previous experiment for the method. Silver fluoride Soluble in water.

2. Inspection of chlorine, bromine and iodine compounds

(1) Displacement reaction among chlorine, bromine and iodine: put 3ml of potassium chloride, potassium bromide, potassium iodide solution and 1ml of gasoline in three tubes respectively. Add each of the newly prepared Chlorine water 2 ml, shake. After the two layers of liquid are stratified, the gasoline layer in the potassium chloride tube is colorless, Potassium bromide The inside of the tube is reddish brown, potassium iodide The inside of the tube is purplish red. This indicates that Chlorine water Bromide and iodide can be identified by displacement method.

Take another two test tubes, each containing 3ml of potassium iodide starch solution, one adding chlorine water and one adding bromine water, and find that both tubes appear blue. It shows that this method can be used to detect iodine in iodide.

(2) Reaction of halides to concentrated sulfuric acid: put a little of potassium chloride, potassium bromide and potassium iodide respectively in three test tubes, and add 1ml of concentrated sulfuric acid respectively. Slightly heating, white fog is generated in the test tube containing potassium chloride; In Sheng Potassium bromide There is a brownish red gas in the test tube, which is bromine vapor; In the test tube containing potassium iodide, purple vapor appears. This is Iodine vapor 。

(3) Reaction of halides to silver nitrate: put 3ml of potassium chloride, potassium bromide and potassium iodide respectively in three test tubes, drop silver nitrate solution into droppers respectively, and shake while dropping. There are white, light yellow and yellow precipitates in the three tubes, which are Silver chloride 、 Silver bromide and Silver iodide 。

Metal halide

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All metals can form halides. Most halides of alkali metals, alkaline earth metals and lanthanide and actinide elements belong to Ions Type or near ionic type, such as NaX, BaCl two ，LaCl three Etc. When Yin and Yang Ionic polarization When the effect is obvious, it shows certain Covalent Sex, such as AgCl, etc. A little high Oxidation value The metal halides of Covalent Type halides, such as AlCl three ，SnCl four ，FeCl three ，TiCl four Etc.

Different types of halides have different properties, as shown in the table below:

Halide type Ionic covalent type

Melting point

Solubility: mostly soluble in water, soluble in organic solvents

Conductive aqueous solution, molten conductive non-conductive

In metal halides, the corresponding hydroxide that is not strong base is easy to hydrolyze, and the product is hydroxide or alkali salt. Those that need special memory are:

SnCl two + H two O → Sn(OH)Cl + HCl

SnCl three + H two O → SnOCl + 2HCl

BiCl three + H two O → BiOCl + 2HCl

Nonmetallic halide

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Nonmetallic boron, carbon, silicon, nitrogen, phosphorus, etc. can form various corresponding halides with halogens. These halides are covalent non-metallic halide hydrolysates, which are generally two acids, such as BX three ，SiX four ，PCl three Etc.

Polyhalide

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Some metal halides can be used in addition to halogen simple substances or halogen compounds, and the resulting compounds are called polyhalides. For example: KI three ，KICl two ，KI two Cl, KIBrCl, etc.

The spatial configuration of polyhalide anions containing three halogen atoms is almost linear. If the halogen atoms are different radius The larger halogen atoms are in the middle, while the smaller halogen atoms are on both sides.

I two With I - The solubility in the solution of is much higher than that in pure water, which is related to the formation of polyhalides, that is, the following addition reaction occurs:

KI + I two → KI three

Anion configuration of polyhalide

For example, according to the price level Electronics For the mutual exclusion theory, VP=(7+1+1+1)/2=5, and the valence shell electron pair space configuration is a triangular cone pair. There are 5-2=3 pairs of anions in each pair Lone pair electron So the spatial configuration of the molecule is linear.

Halide mineral

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Halogen compounds are compounds in which metal element cations interact with halogen element anions (fluorine, chlorine, bromine, iodine, astatine). There are about 120 kinds of halogen compound minerals, mainly fluoride and chloride Bromide and Iodide It is extremely rare.

Due to the different properties of halide compound ions and bond types in mineral structures, the physical properties of various halogen compounds are also different (see the following table). In addition, because the anion radii (I ->Br ->Cl ->F -) of halogen compounds are different, it significantly affects the cation Selection of. Fluorine Ionic radius Smallest, which is mainly related to the cation Ca with smaller radius 2+ 、Mg 2+ And other stable compounds, and most of them are insoluble in water; However, chlorine, bromine and iodine have larger ionic radius, and they are always in contact with cation K with larger radius + 、Na + And other compounds that are easily soluble in water. stay hardness The hardness of fluoride is generally higher than that of chloride Bromide Iodide is high. Among them, the hardness of fluor magnesite is 5, which is the largest hardness in this category of minerals.

Metal halide lamp

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A high brightness discharge lamp, the color rendering index is greater than 75, the lumen rating per watt is greater than 90, the relevant color temperature is 3500 ～ 4040K, and the irradiance is greater than 17W/m2. The lamp includes: a glass shell and a pair of electrical conductors inside; A quartz discharge tube is arranged in the housing. The discharge tube has a electric arc The cavity has a oblong structure with a main diameter and a given arc distance. The ratio of the main diameter to the arc distance is less than 1 and more than 0.9; And an arc generation and maintenance medium is placed in the arc cavity, which includes sodium, scandium, lithium, thulium and thallium halides, the filling gas is selected from argon and xenon, and a given amount of mercury.^[2]

Explosion proof halide lamp

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Explosion proof halide lamp is an integrated explosion-proof projection lamp with high luminous efficiency, which is suitable for construction lighting in explosion-proof areas. The light source is metal halide and high pressure sodium double end fixed lamp tube. The lamp holder sockets at both ends are made of spring structure and other processes. The light transmission is made of 8mm tempered glass in strict accordance with national standards. Advanced technology and leading technology. It has reliable safety performance and is easy to install and move. It is the best lighting fixture in dangerous places such as oil fields, mines, oil depots, gas stations, etc.^[3]

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