Which of the following does not contain a metallic element ?

Options

A. Sodium chloride
B. Silicon dioxide
C. Magnesium oxide
D. Calcium hydroxide

Explanation

To determine which of the following compounds does not contain a metallic element, we will analyze each option one by one.

### Step-by-Step Solution:

1. **Identify the Compounds:**
- A: Sodium Chloride (NaCl)
- B: Silicon Dioxide (SiO2)
- C: Magnesium Oxide (MgO)
- D: Calcium Hydroxide (Ca(OH)2)

2. **Analyze Option A: Sodium Chloride (NaCl):**
- Sodium (Na) is a metal.
- Therefore, Sodium Chloride contains a metallic element.
- **Conclusion:** This option is incorrect.

3. **Analyze Option B: Silicon Dioxide (SiO2):**
- Silicon (Si) is a metalloid, which has properties of both metals and non-metals.
- Oxygen (O) is a non-metal.
- Since Silicon is considered a metalloid and not a pure metal, this compound does not contain a metallic element in the traditional sense.
- **Conclusion:** This option is correct; it does not contain a metallic element.

4. **Analyze Option C: Magnesium Oxide (MgO):**
- Magnesium (Mg) is a metal.
- Therefore, Magnesium Oxide contains a metallic element.
- **Conclusion:** This option is incorrect.

5. **Analyze Option D: Calcium Hydroxide (Ca(OH)2):**
- Calcium (Ca) is a metal.
- Therefore, Calcium Hydroxide contains a metallic element.
- **Conclusion:** This option is incorrect.

### Final Answer:
The compound that does not contain a metallic element is **B: Silicon Dioxide (SiO2)**.

---