How many of the follosing s-block elements to do not give characteristics colours in the flame test
Li,Be,Ca,Sr,Mg,Na,K,Ba

Explanation

To determine how many of the given s-block elements do not give characteristic colors in the flame test, we will analyze each element one by one.

### Step-by-Step Solution:

1. **List the Elements**: The elements provided are:
- Lithium (Li)
- Beryllium (Be)
- Calcium (Ca)
- Strontium (Sr)
- Magnesium (Mg)
- Sodium (Na)
- Potassium (K)
- Barium (Ba)

2. **Identify Flame Colors**:
- **Lithium (Li)**: Gives a crimson red color.
- **Beryllium (Be)**: Does not impart any color.
- **Calcium (Ca)**: Gives a brick red color.
- **Strontium (Sr)**: Gives a crimson red color.
- **Magnesium (Mg)**: Does not impart any color.
- **Sodium (Na)**: Gives a bright yellow color.
- **Potassium (K)**: Gives a violet color.
- **Barium (Ba)**: Gives an apple green color.

3. **Count the Elements with No Color**: From the analysis:
- Beryllium (Be) - No color
- Magnesium (Mg) - No color

Thus, there are **2 elements** (Beryllium and Magnesium) that do not give characteristic colors in the flame test.

4. **Conclusion**: The total number of s-block elements that do not impart characteristic colors in the flame test is **2**.

### Final Answer:
**2 elements (Beryllium and Magnesium) do not give characteristic colors in the flame test.**