Question

Given below are two statements : One is labelled as $AssertionA$ and the other is labelled as $ReasonR$.

$AssertionA$ : Lithium halides are some what covalent in nature.

$ReasonR$ : Lithium possess high polarisation capability.

In the light of the above statements, choose the most appropriate answer from the options given below

JEE MAIN 2021

• A. Both $A$ and $R$ are true and $R$ is the correct explanation of $A$
• B. Both $A$ and $R$ true but $R$ is NOT the correct explanation of $A$
• C. $A$ is false but $R$ is true
• D. $A$ is true but $R$ is false

Answer 1

The correct option is A Both $A$ and $R$ are true and $R$ is the correct explanation of $A$

In alkali series going down the group, the size of the ion increases and the electropositive character increases which makes it more ionic in nature. According to Fajan's rule, due to smaller size of lithium, it has high polarising power which makes LiCl more covalent in nature.
All alkali metals are soft and they can be easily cut through a knife except $Li$. $Li$ is hard due to its anomalous behaviour. This is due to its exceptional smaller size and higher polarising power.