Which of the following ion is diamagnetic? — Atomic Structure Chemistry Question

💡 Solution & Explanation

A species is diamagnetic if all of its electrons are paired (0 unpaired electrons). Let's evaluate the ground-state electronic configurations of the given transition metal ions: (a) Sc^3+ (Z = 21): Scandium has ground configuration [Ar] 3d^1 4s^2. Removing 3 electrons leaves [Ar] 3d^0, which is the closed-shell configuration of argon. It has 0 unpaired electrons and is diamagnetic. (b) Ti^2+ (Z = 22): titanium ion is [Ar] 3d^2 => 2 unpaired electrons (paramagnetic). (c) V^3+ (Z = 23): vanadium ion is [Ar] 3d^2 => 2 unpaired electrons (paramagnetic). (d) Fe^2+ (Z = 26): iron ion is [Ar] 3d^6 => 4 unpaired electrons (paramagnetic). Thus, Sc^3+ is the only diamagnetic ion.