Which of the following ion have the same number of unpaired electrons as in Fe^2+ (Z = 26)? — Atomic Structure Chemistry Question

💡 Solution & Explanation

Fe^2+ (Z = 26) is formed by removing two 4s electrons from the neutral iron configuration ([Ar] 3d^6 4s^2), leaving Fe^2+ = [Ar] 3d^6. In the five degenerate d-orbitals, 6 electrons are distributed as: 1 paired orbital and 4 unpaired orbitals, so n = 4 unpaired electrons. Let's analyze the options: (a) Fe^3+ = [Ar] 3d^5: 5 unpaired electrons. (b) Ni^2+ (Z = 28) = [Ar] 3d^8: 2 unpaired electrons. (c) Co^3+ (Z = 27) = [Ar] 3d^6 (since Co = [Ar] 3d^7 4s^2, removing three electrons yields [Ar] 3d^6): 4 unpaired electrons. (d) Cr^+ (Z = 24) = [Ar] 3d^5 (since Cr = [Ar] 3d^5 4s^1): 5 unpaired electrons. Thus, Co^3+ has the same number of unpaired electrons (4) as Fe^2+.