Question

Assertion :Al and Ga are trivalent in their compounds but monovalent compounds are the most stable down the 13th group. Reason: Down the group (13th), the stability of +3 state decreases and that of +1 state increases due to the prominent "inert pair" effect.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Down the group (13th), the stability of +3 state decreases and that of +1 state increases due to the prominent "inert pair" effect.
$A{I}^{3+}>G{a}^{3+}>I{n}^{3+}>T{I}^{3+}$
$Moststable\underset{stability}{\to }leststable$
$T{I}^{+}>I{n}^{+}>G{a}^{+}>A{I}^{+}$

The inert s-pair effect is significant in group 13 elements. It results in variety of oxidation states. In lighter elements +3 state is the most stable but +1 state increases with atomic number. This inert pair effect is maximum in thallium.