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

💡 Solution & Explanation

# Finding the Effective Atomic Number (EAN) **Step 1: Identify the central metal atom** - Nickel (Ni) is the central atom - Atomic number of Ni = 28 **Step 2: Determine the oxidation state of Ni** - In $[Ni(CN)_4]^{2-}$, cyanide $(CN)^-$ is a neutral ligand in coordination chemistry - With 4 cyanide ligands: $4 \times 0 = 0$ contribution - Charge balance: $x + 4(0) = -2$, so Ni has oxidation state **+2** **Step 3: Count electrons from Ni²⁺** - Ni²⁺ has lost 2 electrons: $28 - 2 = 26$ electrons **Step 4: Count electrons donated by ligands** - Each $CN^-$ ligand donates 1 electron (it's a monodentate σ-donor) - 4 cyanide ligands donate: $4 \times 2 = 8$ electrons **Step 5: Calculate EAN** $$\text{EAN} = 26 + 8 = 34$$ This equals the atomic number of krypton (Kr), giving the complex excellent stability—consistent with the strong-field nature of cyanide ligands. **Answer: EAN = 34**