The correct statements from the following are :
(A) Tl³⁺ is a powerful oxidising agent
(B) Al³⁺ does not get reduced easily
(C) Both Al³⁺ and Tl³⁺ are very stable in solution
(D) Tl¹⁺ is more stable than Tl³⁺
(E) Al³⁺ and Tl¹⁺ are highly stable
Choose the correct answer from the options given below :

Solution

Chemistry ma’am · 3 steps

Thallium feels the inert pair effect: +1 is its comfortable state, so Tl³⁺ grabs electrons.

1. Inert pair effect. Down group 13, the ns² pair takes part in bonding less and less. Aluminium uses all three valence electrons, so +3 is its stable state. Thallium tends to keep its 6s² pair, so +1 is its stable state.
2. What that means. Al³⁺ is already in its preferred state, so it does not get reduced easily (E°_(Al³⁺/Al) = -1.66 V). Tl³⁺ wants to fall back to Tl⁺ by taking two electrons, so it is a strong oxidising agent (E°_(Tl³⁺/Tl⁺) = +1.25 V).

   Statement	Verdict	Reason
   (A) Tl³⁺ is a powerful oxidising agent	True	It readily gains 2e⁻ to become the stable Tl⁺
   (B) Al³⁺ does not get reduced easily	True	+3 is aluminium's stable state; large negative E°
   (C) Al³⁺ and Tl³⁺ both very stable in solution	False	Tl³⁺ is unstable; it gets reduced to Tl⁺
   (D) Tl⁺ more stable than Tl³⁺	True	Inert pair effect is strongest in thallium
   (E) Al³⁺ and Tl⁺ are highly stable	True	Each is the preferred state of its element

3. So. Statements (A), (B), (D) and (E) are correct and only (C) is wrong, which is option (a).

The idea to keep. Down group 13, the +1 state gets more stable. A heavy element's ion stuck in its higher state, like Tl³⁺, is a strong oxidising agent.

Answer from the NTA final answer key. Solution by PrepWiser.