Which of the following metal ions is expected to be coloured?

Options

A. `Zn^(2+)`
B. `Ti^(3+)`
C. `Sc^(3+)`
D. `Ti^(4+)`

Answer

To determine which of the given metal ions is expected to be colored, we need to analyze the electronic configurations of each ion and check for the presence of unpaired electrons, particularly in their d orbitals.

### Step-by-Step Solution:

1. **Identify the Metal Ions**: The metal ions given are Zinc (Zn²⁺), Titanium (Ti³⁺), and Scandium (Sc³⁺).

2. **Determine the Electronic Configuration**:
- **Zinc (Zn²⁺)**: The atomic number of Zinc is 30. The electronic configuration of neutral Zinc is [Ar] 3d¹⁰ 4s². When it loses two electrons to form Zn²⁺, it loses the 4s electrons first, resulting in the configuration [Ar] 3d¹⁰. This means all d electrons are paired.
- **Titanium (Ti³⁺)**: The atomic number of Titanium is 22. The electronic configuration of neutral Titanium is [Ar] 3d² 4s². For Ti³⁺, it loses three electrons (two from 4s and one from 3d), resulting in the configuration [Ar] 3d¹. This indicates one unpaired electron.
- **Scandium (Sc³⁺)**: The atomic number of Scandium is 21. The electronic configuration of neutral Scandium is [Ar] 3d¹ 4s². For Sc³⁺, it loses three electrons (two from 4s and one from 3d), resulting in the configuration [Ar] 3d⁰. This means all d electrons are paired.

3. **Analyze for Color**:
- Colored ions typically have unpaired electrons in their d orbitals, which allow for d-d transitions or charge transfer transitions.
- **Zn²⁺**: No unpaired electrons (3d¹⁰) → Not colored.
- **Ti³⁺**: One unpaired electron (3d¹) → Colored.
- **Sc³⁺**: No unpaired electrons (3d⁰) → Not colored.

4. **Conclusion**: Among the given metal ions, only **Titanium (Ti³⁺)** is expected to be colored due to the presence of an unpaired electron in its d orbital.

### Final Answer:
**Titanium (Ti³⁺) is expected to be colored.**

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