The elements which exist in the liquid state at rooom temperature are.

Options

A. `Na`
B. `Br_2`
C. `Hg`
D. `Ga`

Answer

To determine which elements exist in the liquid state at room temperature, we will analyze the given elements: sodium, bromine, mercury, and gallium.

### Step-by-Step Solution:

1. **Identify Room Temperature**: Room temperature is generally considered to be around 20-25 degrees Celsius (68-77 degrees Fahrenheit).

2. **Check the State of Each Element**:
- **Sodium (Na)**: Sodium is a metal that has a melting point of about 98 degrees Celsius. Therefore, at room temperature, sodium is in the solid state.
- **Bromine (Br)**: Bromine is a non-metal that has a melting point of approximately -7.2 degrees Celsius. Thus, at room temperature, bromine is in the liquid state.
- **Mercury (Hg)**: Mercury is a metal with a melting point of about -38.83 degrees Celsius. Therefore, mercury is also in the liquid state at room temperature.
- **Gallium (Ga)**: Gallium has a melting point of about 29.76 degrees Celsius. At room temperature, gallium can exist in a liquid state, especially if the temperature is slightly above its melting point.

3. **Conclusion**: Based on the analysis:
- Sodium is solid at room temperature.
- Bromine is liquid at room temperature.
- Mercury is liquid at room temperature.
- Gallium can be liquid at room temperature depending on the exact temperature.

Thus, the elements that exist in the liquid state at room temperature are **bromine, mercury, and gallium**.

### Final Answer:
The elements which exist in the liquid state at room temperature are **bromine (Br), mercury (Hg), and gallium (Ga)**.

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