Question

Calculate the charge number of the complex ion:

[Co(NH₃)₄Cl₂]⁺

Answer 1

Complex: [Co(NH₃)₄Cl₂]⁺

Let the oxidation number of Co be x.

NH₃ (neutral ligand) has a charge of 0 each.

There are 4 NH₃ ions, so total charge from ligands = 4 × (0) = 0.

Cl⁻ is a monodentate anionic ligand that has a charge of −1 each.

There are 2Cl⁻ ions = −2

Overall charge on the complex = +1

x + 4(0) + 2(−1) = +1

x − 2 = +1

x = +3

The oxidation number of Co is +3.