(a) What type of isomerism is shown by the complex `[Co(NH_(3))_(5)(SCN)]^(2+)`?
(b) why is `[NiCl_(4)]^(2-)` paramagnetic while `[Ni(CN)_(4)]^(2-)` is diamagnetic ? (Atomic number of Ni=28)
(c) Why are low spin tetrahedral complexes rarely observed?

Explanation

Let's break down the solution to the question step by step.

### (a) What type of isomerism is shown by the complex `[Co(NH₃)₅(SCN)]²⁺`?

1. **Identify the Ligands**: The complex contains ammonia (NH₃) and thiocyanate (SCN⁻).
2. **Recognize the Ambidentate Nature of SCN⁻**: The thiocyanate ion can bind to the metal through either the sulfur (S) or the nitrogen (N) atom, making it an ambidentate ligand.
3. **Determine the Type of Isomerism**: The presence of an ambidentate ligand leads to the possibility of linkage isomerism, where the same ligands are coordinated to the metal ion in different ways.
4. **Conclusion**: Therefore, the complex `[Co(NH₃)₅(SCN)]²⁺` exhibits linkage isomerism.