What is the Primary and Secondary valency of Ni in \([Ni(NH_3)_6]Cl_2\)?

2, 6

The correct answer is option 2. 2, 6.

To determine the primary and secondary valency of nickel (Ni) in the complex \([Ni(NH3)_6]Cl_2\), let us break it down:

1. Primary Valency: The primary valency corresponds to the oxidation state of the central metal ion. In this complex, the nickel ion is surrounded by six ammonia (NH\(_3\)) ligands and is balanced by two chloride (Cl\(^-\)) ions outside the coordination sphere.

The complex \([Ni(NH3)_6]^{2+}\) is neutralized by 2 Cl\(^-\) ions, which indicates the oxidation state of Ni is +2. Therefore, the primary valency (oxidation state) of Ni is 2.

2. Secondary Valency: The secondary valency corresponds to the coordination number, which is the number of ligands directly bonded to the metal ion. In this complex, there are six ammonia (NH\(_3\)) ligands directly bonded to the nickel ion. Therefore, the secondary valency (coordination number) of Ni is 6.

So, the primary and secondary valency of Ni in \([Ni(NH3)_6]Cl_2\) are 2 and 6 respectively.