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

💡 Solution & Explanation

# Finding Effective Atomic Number (EAN) **Step 1: Identify the central metal atom** - Nickel (Ni) is the central atom - Atomic number of Ni = 28 - Electrons in neutral Ni = 28 **Step 2: Account for the charge on the complex** - The complex has a 2− charge - This means 2 extra electrons are present in the system - Electrons from complex = 28 + 2 = 30 **Step 3: Count electrons from ligands** - Ligand: $CN^-$ (cyanide) - Each $CN^-$ donates 1 lone pair = 2 electrons per ligand - Number of $CN^-$ ligands = 4 - Electrons from ligands = 4 × 2 = 8 **Step 4: Calculate EAN** $$\text{EAN} = \text{(electrons from metal)} + \text{(electrons from ligands)}$$ $$\text{EAN} = 30 + 8 = 38$$ **Verification:** EAN of 38 corresponds to the electronic configuration of Krypton (Kr), which is a noble gas configuration. This indicates high stability of $[Ni(CN)_4]^{2-}$, consistent with $Ni^{2+}$ adopting a square planar geometry with strong-field $CN^-$ ligands. **Answer: EAN = 38**