Explain, with suitable examples, the following:
(i) Electron-deficient.

Explanation

`to` Molecular hydrides (or) covalent hydrides are formed by the p-block elements.
`to` These molecular hydrides are divided into three types:
i) Electron deficient hydrides
ii) Electron - precise hydrides
iii) Electron - rich hydrides
i) Electron - deficient hydrides : These are the molecular hydrides in which the available no. of valency electrons is less than the number required for normal covalent bond formation.
(or)
These are the molecular hydrides in which the available valency electrons are lessthan the required for writting the Lewis structure of the molecule.
Eg : `(AlH_(3))_(n),B_(2)H_(6)` etc.
`to` These hydrides acts as Lewis acids i.e. electron pair acceptors. These forms dative bond with donors.
ii) Electron - precise hydrides : These are the molecular hydrides in which all the valency electrons of the central atom are involved in bond formation.
(or)
These are the molecular hydrides which contains the required no. of valency electrons to write the Lewis structure of the molecule.
Eg : Group 14 elements forms this type of hydrides `CH_(4),C_(2)H_(6)`, etc., are examples of this type.
`to` These have tetrahedral geometry.
iii) Electron - rich hydrides :
`to` These are the molecular hydrides in which the valency electrons on the central atom are more than that are required for bond formation.
(or)
These are the molecular hydrides in which the available valency electrons are more than the required for writting the Lewis structure of the molecule.
`to` These hydrides contains lone pairs on central atoms.
Eg :
`to` These hydrides have high boiling points than those of the hydrides of the subsequent members of group because of hydrogen bond formation.