Question

Assertion :Statement $-$ 1: Boron does not show univalent nature but unipositive nature of thallium is quite stable. Reason: Statement $-$ 2 : Inert pair effect predominates in thallium.

• A. Statement $-$ 1 is true, Statement $-$ 2 is true and Statement $-$ 2 is correct explanation for Statement $-$ 1.
• B. Statement $-$ 1 is true, Statement $-$ 2 is true and Statement $-$ 2 is not the correct explanation for Statement $-$ 1.
• C. Statement $-$ 1 is true, Statement $-$ 2 is false.
• D. Statement $-$ 1 is false, Statement $-$ 2 is true.

Answer 1

The correct option is A Statement $-$ 1 is true, Statement $-$ 2 is true and Statement $-$ 2 is correct explanation for Statement $-$ 1.

The inertness of s subshell electrons towards the bond formation is called inert pair effect or it can be said as the inactiveness of electrons present in outermost shell (i.e. $n{s}^2$) to get unpaired and involve in bond formation is called inert pair effect.

for example:

1) In 13th group, thallium can exhibit $+1$ and $+3$ oxidation states but it is stable in $+1$ oxidation state only due to inert pair effect

2) In 14th group , lead shows both $+2$ and $+4$ oxidation states but it is stable in $+2$ oxidation state due to inert pair effect.

3)In group 15 elements,(Bi) the stability of $+3$ oxidation state increases down the group and that of $+5$ oxidation state decreases down the group, due to inert pair effect."