Electron-deficient: the hydrides which contain less than eight electron in their outmost shell are called electron- deficient for exam B2H6
Electron- precise: These hydrides contain exact number of electron to form covalent bonds and hence are called as electron-precise hydrides for example: CH4, SIH4,GeH4,SnH4
Electron-rich: these have more electron than required to form nomal covalent bond and are called as electron rich hydrides. For example NH3,PH3,H2O,H2S.