Why `Zn^(2+)` ions are colourless while `Ni^(2+)` ions are green and `Cu^(2+)` ions are blue in colour?

Explanation

### Step-by-Step Solution:

1. **Understanding Electronic Configurations**:
- The electronic configuration of an atom describes the distribution of electrons in its atomic orbitals. For transition metals, the d-orbitals play a crucial role in determining the color of the ions.

2. **Zinc Ion (`Zn^(2+)`)**:
- The electronic configuration of zinc (Zn) is:
\[
...