Explain the types of covalent hydrides with examples.
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
H O H, H N H, H F:
(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,
PH3 H2O NH3
Phosphane oxidane ozane