The correct order of increasing ionic character among $\mathrm{LiH}, \mathrm{NaH}, \mathrm{KH}, \mathrm{RbH}…

The correct order of increasing ionic character among $\mathrm{LiH}, \mathrm{NaH}, \mathrm{KH}, \mathrm{RbH}, \mathrm{CsH}$ is
  1. $\mathrm{LiH} < \mathrm{NaH} < \mathrm{CsH} < \mathrm{KH} < \mathrm{RibH}$
  2. $\mathrm{LiH} < \mathrm{NaH} < \mathrm{KH} < \mathrm{RibH} < \mathrm{CsH}$
  3. $\mathrm{PbH} < \mathrm{CsH} < \mathrm{NaH} < \mathrm{KH} < \mathrm{LiH}$
  4. $\mathrm{NaH} < \mathrm{CsH} < \mathrm{Rb}-\mathrm{H} < \mathrm{LiH} < \mathrm{KH}$

Solution

According to Fajan's rule, the size of the cations increase down a group and also, the increase in size of an atom increases the ionic molecules formed. Caesium being lowest down the group has most ionic character, followed by rubidium, potassium, sodium and lithium respectively. $ \mathrm{LiH} < \mathrm{NaH} < \mathrm{KH} < \mathrm{RbH} < \mathrm{CsH} . $ Hence, the correct option is (2)

Asked in: AP EAMCET 2020 (22 Sep Shift 1)

Practice more Chemical Bonding and Molecular Structure questions on Aicharya