Chemistry - s Block Elements Question with Solution | TestHub

The stability of alkali metal hydrides decreases from Li to Cs. It is due to the fact that $\mathrm{M}-\mathrm{H}$ bonds becomes weaker with increase in size of alkali metals as we move down the group from $\mathrm{Li}$ to $\mathrm{Cs}$. Thus the order of stability of hydrides is $\mathrm{LiH}>\mathrm{NaH}>\mathrm{KH}>\mathrm{RbH}>\mathrm{CsH}$