The **Effective Atomic Number (EAN)** of Co in $[Co(NH_3)_6]^{3+}$ (Z(Co) = 27) is:
- 36 (krypton config, EAN rule obeyed)
- 35
- 27
- 30
Show answer and solution
Correct answer: A. 36 (krypton config, EAN rule obeyed)
EAN = Z − (oxidation state) + (electron pairs from ligands × 2) = 27 − 3 + 6(2) = 36 = electron count of Kr. EAN rule obeyed.