Explain the types of covalent hydrides with examples

CBSE Class 11
1

Explain the types of covalent hydrides with examples.

2

Hydrogen forms molecular compounds with p-block elements (B, C, N, O, F; Si, P, S, Cl; Ga, Ge, As, Sb, Br; In, Sn, Sb, Te, I; Tl, Pb, At). The common examples of such hydrides are CH3, NH3, H2O, HF etc.

Covalent hydrides are classified as electron rich, electron precise and electron deficient hydrides.
a) Electron rich molecular hydrides: These hydrides have one or more lone pairs of electrons around the central more electronegative element. For example

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H � O � H, H � N � H, H � F:

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H

b) Electron precise molecular hydrides: Elements of group 14 form such hydrides. The bond length increases on going down the group. A common example of electron precise molecular hydrides is CH4.
c) Electron deficient molecular hydrides: These hydrides have lesser number of electrons than that required for writing the conventional Lewis structure. A common example of such molecular hydride is diborane, B2H6.
d) Systematic names of molecular hydrides: The systematic names of these hydrides are obtained from the name of the element and the suffix �ane. For example,

   PH<sub>3</sub>           H<sub>2</sub>O          NH<sub>3</sub>

Phosphane oxidane ozane