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: Group 13 Elements.
Group 13 elements (B, Al, Ga, In, Tl) typically exhibit a +3 oxidation state.
Step 2: Inert Pair Effect Explained.
In heavier Group 13 elements, such as Tl, the ns\(^2\) electrons are less likely to participate in bonding due to ineffective shielding and relativistic effects. This results in a stable +1 oxidation state (monovalency).
Step 3: Summary.
The inert pair effect explains the presence of monovalency in Group 13 elements.
Final Answer: \[ \boxed{\text{Inert Pair effect}} \]