Write the expected formulas for the hydrides of `4^(th)` period elements.What is the trend in the formulas? In what way the first two numbers of the series different from the others ?

Explanation

he expected formulas for the hydrides of `4^(th)` period elements `MH_4` ( electron precise) `M_2H_6` ( electron deficient) and `MH_3` ( electron rich) The trend is formula is
(i) Electron precise hydries-`CH_4C_2H_6,SiH_4,Geh_4`
(ii) Electron deficient hydrides-`B_2H_6`
(iii) Electron rich hydrides -`NH_3,H_2O`
The first two members of the series KH, `CaH_2` are ionic hydrides whereas the other members of the series `CH_4,C_2H_6, SiH_4, B_2H_6, NH_3` are covalent hydrides.