Question

In $IIIA$ group, $Tl$(thallium) shows $+1$ oxidation state while other members show $+3$ oxidation state. Why

• A. Presence of lone pair of electron in $Tl$
• B. Inert pair effect
• C. Large ionic radius of $Tl$ ion
• D. None of these

Answer 1

Answer: (B)

Inert pair effect become significant for the sixth and seventh period of $p$ -block element.