Answer:
Central-metal oxidation state: +2
Coordination number: 6
Overall charge: -2
Explanation:
In the ion complex:
Na₂[Cr(NH₃)₂(NCS)₄]
The central-metal is Cr, the ligands are NH₃ and NCS.
The NH₃ is a neutral ligand, while NCS is an anionic ligand with -1 in charge.
The overall charge of the complex is:
2Na⁺ + [Cr(NH₃)₂(NCS)₄]⁻² → -2
As NCS gives -1 in charge and there are four NCS, The Cr must be in +2 of oxidation state to give an overall charge of -2.
As Cr is bonded to 2 NH₃ and 4 NCS, the coordination number is 2+4 = 6
I hope it helps!
