Question

What is the coordination number in complexes?

• A. Number of Ligands in the coordination sphere.
• B. Number of coordinate bonds formed by the central metal with ligands.
• C. Number of ions in the compound.
• D. Number of atoms in the ligand.

Hint:

Coordination number counts the coordinate bonds from ligands to the central metal, not the number of ligands.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept
In a complex, ligands donate electron pairs to the central metal atom or ion through coordinate bonds.

Step 2: Define the term
Coordination number is the total number of coordinate bonds formed between the central metal and the ligands, that is the number of donor atoms attached.

Step 3: Compare the options
A bidentate ligand such as ethylenediamine forms two bonds, so counting ligands alone is wrong. Option (B) is correct.

Final Answer:
Coordination number is the number of coordinate bonds from the ligands to the metal. \[ \boxed{\text{(B) }\text{Number of coordinate bonds formed by the central metal with ligands.}} \]