Which of the following compounds is coloured?

Options

A. `TiCl_(3)`
B. `FeCl_(3)`
C. `CoCl_(2)`
D. All of these

Explanation

To determine which of the given compounds is colored, we need to analyze the electronic configurations of the metal ions present in each compound. The compounds given are TiCl3, FeCl3, CoCl2, and an option stating "all of these."

### Step-by-Step Solution:

1. **Analyze TiCl3:**
- Titanium (Ti) has an atomic number of 22. Its electronic configuration is \( \text{[Ar]} 3d^2 4s^2 \).
- In TiCl3, titanium is in the +3 oxidation state (Ti^3+).
- The electronic configuration of Ti^3+ is obtained by removing 3 electrons: \( \text{[Ar]} 3d^1 4s^0 \).
- The d-orbital configuration has 1 unpaired electron (3d^1), which can lead to d-d transitions, thus TiCl3 is colored.

2. **Analyze FeCl3:**
- Iron (Fe) has an atomic number of 26. Its electronic configuration is \( \text{[Ar]} 3d^6 4s^2 \).
- In FeCl3, iron is in the +3 oxidation state (Fe^3+).
- The electronic configuration of Fe^3+ is \( \text{[Ar]} 3d^5 4s^0 \).
- The d-orbital configuration has 5 unpaired electrons (3d^5), which also allows for d-d transitions, thus FeCl3 is colored.

3. **Analyze CoCl2:**
- Cobalt (Co) has an atomic number of 27. Its electronic configuration is \( \text{[Ar]} 3d^7 4s^2 \).
- In CoCl2, cobalt is in the +2 oxidation state (Co^2+).
- The electronic configuration of Co^2+ is \( \text{[Ar]} 3d^7 4s^0 \).
- The d-orbital configuration has 3 unpaired electrons (3d^7), which allows for d-d transitions, thus CoCl2 is colored.

4. **Conclusion:**
- All three compounds (TiCl3, FeCl3, and CoCl2) are colored due to the presence of unpaired electrons in their d-orbitals, which can participate in d-d transitions.
- Therefore, the final answer is **D: All of these**.