How many of the following are electron deficient HydridesCH4,SiH4,AlH3,GaH3,C2H6,NH3,H2O,B2H6

IIIA – group hydrides are electron deficient hydride the molecular hydrides which have less number of valency electrons in central atom to form chemical bond are called electron deficient. Remember silicon hydride obeys octet, but it can accept nucleophile and form additional bonds.