Question

The EAN of cobalt in the complex \([Co(NH_3)_6]^{3+\) is:}

• A. 27
• B. 30
• C. 33
• D. 36

Hint:

Use EAN = (Atomic number – Oxidation state) + (2 × number of ligands) for quick calculations.

Answer 1

The Correct Option is D

Given: - Atomic number of Co = 27 - Oxidation state of Co in \([Co(NH_3)_6]^{3+}\) is \( +3 \) - Each NH₃ ligand donates 2 electrons (but for EAN, we count only total ligand pairs = 6) \[ \text{EAN} = 27 - 3 + 6 \times 2 = 24 + 12 = \boxed{36} \] Thus, cobalt achieves the effective atomic number of the nearest noble gas (Kr).