Question

The stability of $+1$ oxidation state among $Al$, $Ga$, $In$ and $Tl$ increases in the sequence:

• A. $Tl<In<Ga<Al$
• B. $In<Tl<Ga<Al$
• C. $Ga<In<Al<Tl$
• D. $Al<Ga<In<Tl$

Answer 1

The correct option is D $Al<Ga<In<Tl$

The stability of $+1$ oxidation state among $Al$, $Ga$, $In$ and $Tl$ increases in the sequence.
$Al<Ga<In<Tl$.
This is due to inert pair effect due to which, on moving down the group, the stability of $+3$ oxidation state decreases while the stability of $+1$ oxidation state increases.