Molecular hydrides are classified as electron deficient, electron precise and electron rich compounds. Explain each type with two examples.

Explanation

Molecular hydrides are classified according to the relative numbers of electrons and bonds in Lewis structure as follow
(i) Electron deficient hydrides These type of hydrides contain central atom with incomplete octet. These are formed by 13 group elements, e.g., `BH_(3), AlH_(3)`, etc . To complele their octet they generally exist in polymeric forms such as `B_(2)H_(6), B_(4)H_(10), (AlH_(3))_(n)` etc. These hydrides act as Lewis acids.
(ii) Electron precise hydrides These hydrides have exact number of electrons required to form normal covalent bonds. These are formed by 14 group elements, e.g.`CH_(4), SiH_(4)`, etc These are tetrahedral in shape.
(iii) Electron rich hydrides These hydrides contain central atom with excess electrons, which are present as ione pairs.
These are formed by 15, 16 and 17 group elements, e.g., `NH_(3).H_(2)O,HF` etc. These hydrides act as Lewis bases