The alkali metals form salt-like hydrides by the direct synthesis at elevated temperature. The thermal stability of these hydrides decreases in which of the following orders?

Step-by-step solution

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