How many electrons are present in t2g set of d-orbitals of central metal cation in [Fe(H2O)5(NO)]SO4 — Coordination Compounds Chemistry Question

💡 Solution & Explanation

Step 1: In Hg[Co(SCN)4], the complex anion is [Co(SCN)4]^2-, meaning Cobalt is in the +2 oxidation state (3d^7 configuration) coordinated by weak-field SCN^- ligands. Step 2: With a coordination number of 4, the complex adopts a tetrahedral geometry. The electronic configuration of a d^7 ion in a tetrahedral field is e^4 t_2^3, which has exactly 3 unpaired electrons. Step 3: Using the spin-only formula, μ = \sqrt{n(n+2)} = \sqrt{3(3+2)} = \sqrt{15} BM, which corresponds to option (c).