Coloured salts are formed by

Options

A. Alkali metals
B. Lanthanides
C. Actinides
D. Transition metals

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the formation of colored salts. We need to identify which type of metal is responsible for the formation of these colored salts.

2. **Identifying the Options**: The options provided are:
- Alkaline metals
- Lanthanides
- Actinides
- Transition metals

3. **Analyzing Each Option**:
- **Alkaline Metals**: These metals (like sodium and potassium) typically form colorless salts because they do not have d-electrons that can transition between energy levels.
- **Lanthanides**: While some lanthanides can form colored compounds, they are not as commonly known for this as transition metals.
- **Actinides**: Similar to lanthanides, some actinides can form colored compounds, but they are not the primary group associated with colored salts.
- **Transition Metals**: Transition metals are known for their ability to form colored compounds due to the presence of d-electrons. The d-d transitions of these electrons when they absorb certain wavelengths of light result in the appearance of color.

4. **Conclusion**: Based on the analysis, the correct answer is that colored salts are primarily formed by **transition metals**.

**Final Answer**: Colored salts are formed by transition metals.

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