Question

The secondary valency of Co in the complex \([Co(NH_3)_5(NO_2)]^{2+}\) is

• A. 5
• B. 1
• C. 4
• D. 6

Hint:

In Werner's theory, the secondary valency of the central metal is its coordination number, that is the number of ligand atoms directly attached (coordinated) to the metal.

Answer 1

The Correct Option is D

Step 1: Recall Werner's idea of secondary valency.
In Werner's theory the secondary valency of the central metal is the same as its coordination number, that is the number of ligand atoms directly bonded to the metal.

Step 2: Look at the complex.
The complex is \([Co(NH_3)_5(NO_2)]^{2+}\). The ligands directly attached to cobalt are five \(NH_3\) molecules and one \(NO_2\) group.

Step 3: Count the donor atoms.
Each \(NH_3\) gives one donor atom (5 in total) and \(NO_2\) gives one donor atom. That makes \(5 + 1 = 6\).

Step 4: Connect count to secondary valency.
The coordination number is 6, so the secondary valency of cobalt is 6.

Step 5: Conclude.
The secondary valency of Co in this complex is 6.

\[ \boxed{6} \]