The effective atomic number for the complex ion [Ni(CN)4]2– is — Coordination Compounds Chemistry Question

💡 Solution & Explanation

# Effective Atomic Number (EAN) Calculation for $[Ni(CN)_4]^{2-}$ **Step 1: Identify the central metal atom** - Nickel (Ni) has atomic number 28 - Electronic configuration: $[Ar]3d^8 4s^2$ **Step 2: Determine electrons from the metal** In the complex, Ni exists as $Ni^{2+}$ (after losing 2 electrons from 4s orbital): - Electrons from $Ni^{2+}$ = 28 − 2 = **26 electrons** **Step 3: Count electrons from ligands** - Each $CN^-$ ligand donates 1 electron pair (2 electrons) to the metal - Number of $CN^-$ ligands = 4 - Electrons from ligands = 4 × 2 = **8 electrons** **Step 4: Account for the charge** - Complex has charge $2-$, meaning 2 extra electrons in the system - Additional electrons = **2 electrons** **Step 5: Calculate EAN** $$EAN = 26 + 8 + 2 = 36$$ The EAN is **36**, which equals the atomic number of krypton ($Kr$). This high EAN reflects the strong field nature of $CN^-$ ligands and the stability of this square planar complex.