The correct option is Bromine.
Explanation
Elements in the periodic table are classified as metals, non-metals, or metalloids. At standard room temperature, these elements exist in different physical states (solid, liquid, or gas). While the majority of non-metals are gases or solids, specific exceptions exist regarding their state.
- Bromine (Br): This is the Correct option. Bromine is a non-metal belonging to Group 17 (Halogens). It is the only non-metal that exists as a liquid at room temperature. It appears as a reddish-brown liquid.
- Iodine (I): This is Incorrect. Iodine is a non-metal (Halogen) that exists as a lustrous, dark-grey solid at room temperature. It is known for subliming directly into a violet gas upon heating.
- Mercury (Hg): This is Incorrect. Mercury is a metal, not a non-metal. It is the only metal that exists as a liquid at standard room temperature.
- Chlorine (Cl): This is Incorrect. Chlorine is a non-metal (Halogen) that exists as a greenish-yellow gas at room temperature.
Key Takeaway: Bromine is the unique non-metal found in a liquid state at room temperature, whereas Mercury is the unique metal found in a liquid state under the same conditions.