Which one is gas at room temperature?

Options

A. `CI_(2)`
B. `Br_(2)`
C. `l_(2)`
D. (a) and (b)

Answer

To determine which substance is a gas at room temperature among the given options (A: Chlorine, B: Bromine, C: Iodine, D: A and B), we can analyze the properties of each element.

### Step-by-Step Solution:

1. **Identify the Elements**: We have three elements to consider: Chlorine (Cl), Bromine (Br), and Iodine (I).

2. **Understand Room Temperature**: Room temperature is typically around 20-25 degrees Celsius (68-77 degrees Fahrenheit).

3. **Check Physical States of Each Element at Room Temperature**:
- **Chlorine (Cl)**: Chlorine is a diatomic molecule (Cl2) and is known to be a gas at room temperature. Its boiling point is approximately -34°C, which is well below room temperature.
- **Bromine (Br)**: Bromine is also a diatomic molecule (Br2) but is a liquid at room temperature. Its boiling point is about 59°C, which is above room temperature.
- **Iodine (I)**: Iodine is a diatomic molecule (I2) and is a solid at room temperature. Its boiling point is around 184°C, which is significantly higher than room temperature.

4. **Conclusion**: Based on the boiling points and physical states at room temperature, Chlorine is the only element that exists as a gas at room temperature.

5. **Final Answer**: Therefore, the correct answer is **Option A: Chlorine**.