Question

Explanation for occurrence of monovalency in Group 13 is given by............

• A. Pauli's Exclusion Principle
• B. Hund's Rule
• C. Inert Pair effect
• D. Isotope effect

Hint:

Inert pair effect: reluctance of ns\(^2\) electrons to bond → stable lower oxidation states in heavier p-block elements.

Answer 1

The Correct Option is C

Step 1: Recall Group 13 elements.
Group 13 (B, Al, Ga, In, Tl) usually show +3 oxidation state.
Step 2: Inert pair effect.
In heavier elements (like Tl), the ns\(^2\) electrons become reluctant to participate in bonding due to poor shielding and relativistic effects. This causes a stable +1 oxidation state (monovalency).
Step 3: Conclusion.
Thus, the occurrence of monovalency in Group 13 is explained by the inert pair effect.
Final Answer: \[ \boxed{\text{Inert Pair effect}} \]