Inert Pair Effect & Stability — Tl⁺ vs Tl³⁺ and Al³⁺ Explained (JEE Main)
❓ Question Which of the following statements are correct ? (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) Tl⁺ is more stable than Tl³⁺ (E) Al³⁺ and Tl⁺ are highly stable 🖼️ Question Image ✍️ Short Solution We evaluate each statement using electronic structure, standard electrode potentials and chemical trends (inert-pair effect, stability of Al³⁺). 🔹 (A) Tl³⁺ is a powerful oxidising agent — True Tl in +3 state has electronic configuration [Xe]4f¹⁴5d¹⁰ (6s⁰6p¹ for neutral Tl → Tl³⁺ has lost the 6p and 6s electrons partially). Due to the inert-pair effect , the 6s electrons are reluctant to participate in bonding; Tl³⁺ is stabilized poorly and tends to be reduced to Tl⁺. Thus Tl³⁺ accepts electrons readily → it is a strong oxidizing agent (gets reduced to the more stable Tl⁺). Example: Tl³⁺ is often reduced in aqueous solution; TlCl₃ disproportionates, etc. 🔹 (B) Al³⁺ d...