Which of the following s-block metals do not impart any colour to the flame-

Options

A. `Li,Be`
B. `Cs,Fr`
C. `Be,Mg`
D. `Ba,Ra`

Explanation

To determine which s-block metals do not impart any color to the flame, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the S-Block Elements**:
- The s-block elements consist of Group 1 (alkali metals) and Group 2 (alkaline earth metals) in the periodic table.
- Group 1 includes: Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), and Francium (Fr).
- Group 2 includes: Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra).

2. **Understand Flame Test Colors**:
- When s-block metals are heated in a flame, they emit characteristic colors.
- For example:
- Lithium (Li) - Crimson red
- Sodium (Na) - Yellow
- Potassium (K) - Violet
- Rubidium (Rb) - Red violet
- Cesium (Cs) - Blue
- Calcium (Ca) - Brick red
- Strontium (Sr) - Crimson red
- Barium (Ba) - Apple green

3. **Identify Metals that Do Not Impart Color**:
- From the above list, we need to identify which metals do not impart any color to the flame.
- Beryllium (Be) and Magnesium (Mg) are known to not impart any color during the flame test.

4. **Conclusion**:
- Therefore, the s-block metals that do not impart any color to the flame are **Beryllium (Be)** and **Magnesium (Mg)**.

### Final Answer:
The s-block metals that do not impart any color to the flame are **Beryllium (Be)** and **Magnesium (Mg)**.

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