Which metal is liquid at room temperature and is often used in thermometers?

💡 Solution & Explanation

Mercury is a unique d-block transition metal that remains in a liquid state at standard room temperature and pressure due to its unusually weak metallic bonding and relativistic effects on electrons. Other options such as gallium and cesium have melting points very close to room temperature but are solid under standard conditions, whereas bromine is a liquid non-metal rather than a metal. Mercury has historically been widely utilized in barometers, manometers, and clinical thermometers due to its uniform thermal expansion.