This is not a non-metal.

Options

A. hydrogen
B. silicon
C. mercury
D. chlorine

Explanation

To determine which of the given options is not a non-metal, we will analyze each option based on their properties.

### Step-by-Step Solution:

1. **Identify the Options**: The options given are Hydrogen, Silicon, Mercury, and Chlorine.

2. **Analyze Hydrogen**:
- Hydrogen is a gas at room temperature.
- It does not conduct electricity.
- Therefore, Hydrogen is classified as a non-metal.

3. **Analyze Silicon**:
- Silicon is solid at room temperature.
- It does not exhibit metallic luster and does not conduct electricity well.
- Silicon has properties that are intermediate between metals and non-metals, classifying it as a metalloid.
- Therefore, Silicon is not a non-metal.

4. **Analyze Mercury**:
- Mercury is a liquid at room temperature.
- It has a shiny appearance and conducts electricity.
- Mercury is classified as a metal.
- Therefore, Mercury is not a non-metal.

5. **Analyze Chlorine**:
- Chlorine is a gas at room temperature.
- It does not conduct electricity.
- Therefore, Chlorine is classified as a non-metal.

6. **Conclusion**:
- The options that are not non-metals are Silicon (a metalloid) and Mercury (a metal).
- Thus, both Silicon and Mercury are correct answers to the question of which is not a non-metal.

### Final Answer:
Silicon and Mercury are not non-metals. Silicon is a metalloid, and Mercury is a metal.

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