Which of the following metal(s) do (es) not give characteristic flame colouration?

Options

A. `Ca`
B. `Mg`
C. `Be`
D. `Na`

Answer

To determine which metals do not give characteristic flame coloration, we need to analyze the flame colors produced by each of the alkaline earth metals mentioned in the question.

### Step-by-Step Solution:

1. **Identify the Metals**: The metals we are considering are Calcium, Magnesium, Beryllium, and Sodium.

2. **Flame Color of Calcium**: When calcium is introduced to a flame, it produces a brick red color.

3. **Flame Color of Magnesium**: Magnesium does not produce any characteristic flame color. It burns with a bright white light but does not impart a specific color to the flame.

4. **Flame Color of Beryllium**: Similar to magnesium, beryllium also does not give any characteristic flame coloration.

5. **Flame Color of Sodium**: Sodium produces a bright golden yellow color when introduced to a flame.

6. **Conclusion**: From the analysis, we find that Magnesium and Beryllium do not give characteristic flame coloration.

### Final Answer:
The metals that do not give characteristic flame coloration are **Magnesium and Beryllium**.