What is the coordination number of Ni in [Ni(NH3)6]Cl2?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 6
The coordination number of a metal ion is the number of ligand donor atoms bonded directly to it.
Ligands on Ni: six \( \ce{NH3} \) molecules inside the bracket, each a unidentate ligand binding through its N atom.
Counter ions: the two \( \ce{Cl^-} \) ions are outside the bracket and are not bonded to Ni.
Donor atoms bonded to Ni: 6 × 1 = 6, so the coordination number of Ni is 6.
NCERT (2026-27 edition):
5.2 Definitions of Some Important Terms Pertaining to Coordination Compounds – “The coordination number (CN) of a metal ion in a complex can be defined as the number of ligand donor atoms to which the metal is directly bonded.”