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1.
Inter-halogen compounds
Inter-halogen compounds refer to compounds formed by two or more halogens, such as IF 5 and ICl 3
.
Most inter-halogen compounds are formed by two kinds of halogens, and there are few inter-halogen compounds formed by three kinds of halogen atoms
In interhalogen compounds, the central atom is a halogen electronegativity larger and smaller radii, such as I, Br; coordinating atoms is electronegativity larger and smaller radius halogen, such as CI, F.
.
The number of coordination atoms in the halogen intercompound is usually an odd number, such as IF 7 , BrF 5 , CIF 5 , IBr 3 and so on
The greater the molar mass of the interhalogen compound, the higher its boiling point
.
CIF is a colorless gas, BrF is a red-brown gas, ICI is a brown solid, and IBr is a black solid; CIF 3 is a colorless gas, BrF 3 is a green liquid, and IF 3 is a yellow solid
Inter-halogen compounds are generally obtained by direct combination of halogen elements
.
E.
Interhalogen compounds are easily hydrolyzed in water to generate two acids.
The center with high oxidation number combines with -OH in H 2 O to form oxo acid, and the halogen ligand with low oxidation number combines with H in H 2 O to form hydrogen acid.
ICl+H 2 O=HIO+HCI
BrF 5 +3H 2 O=HBrO 3 +5HF
2.
Polyhalides
Some alkali metal halides with a larger radius combine with elemental halogens to form polyhalides.
For example, elemental iodine is dissolved in the KI solution to form Kl 3
.
The I 2 + the I-the I = .
3 -
Due to the formation of I 3 -, the solubility of I 2 in water increases; as the concentration of I 3 -in the solution increases, the color of the solution gradually darkens from yellow to brownish red
.
Polyhalides can also be obtained by reacting metal halides with interhalogen compounds
.
E.
CsBr+IBr=CsIBr 2
Polyhalides are unstable and decompose when heated
The decomposition product tends to obtain a metal halide formed from a halogen with a relatively large electronegativity, and the metal halide has a large lattice energy and high stability
.
It is not difficult to see that due to the extremely large lattice energy of fluoride, fluorine-containing polyhalides are prone to decomposition, so it is difficult to generate fluorine-containing polyhalides
Polyhalogen anions with large central atomic radius and high symmetry tend to be stable, so the stability is
The I .
3 - > IBr 2 - > the ICI 2 - > the I 2 Br - > Br .
