Write a note on halide compounds of group-16 elements.

Explanation

The elements of group-16 form halides of the type `EX_(6), EX_4` and `EX_2` where E is an element of the group and X is a halogen.
The stability of the halides decreases in the order `F^(-) gt CI^(-) gt Br^(-) gt I^(-)`
. Amongst hexahalides only hexafluorides are stable. All hexafluorides are gaseous in nature. They have octahedral structure.`SF_6` is exceptionally stable.
Amongst tetrafluorides, `SF_4` is a gas, `SeF_4` is a liquid and `TeF_4` is a solid. These fluorides have `sp_3d` hybridisation and thus, have trigonal bipyramidal structures in which one of the equatorial positions is occupied by a lone pair of electrons. The geometry is also regarded as seesaw geometry.
All elements except oxygen form dichlorides and dibromides. These dihalides are formed by `sp^(3)` hybridisation and thus, have tetrahedral structure. The wellknown monohalides are dimeric in nature.
Examples : `S_2F_2, S_2Cl_2, S_2Br_2, Se_2Cl_2` and `Se_2Br_2`. These dimeric halides undergo disproportionation as given below :
`2Se_(2)Cl_(2) to 3Se + SeCl_(4)`