Mercury is the metallic element that is liquid at ordinary room temperature. Its symbol is Hg, from the Latin hydrargyrum, and its atomic number is 80.
Mercury melts at −38.83°C, so it remains liquid in a typical room while most metals are solid. It boils at 356.73°C, giving it a broad liquid range that helped make it useful in thermometers, barometers, switches, and scientific instruments. Its high density and visible expansion with temperature were especially valuable for measurement.
Mercury is found mainly in the ore cinnabar, or mercury(II) sulfide. It is also known as quicksilver, a name referring to its fast-moving, silvery appearance. A common mix-up is bromine: bromine is also liquid at room temperature, but it is a nonmetal halogen, not a metallic element. Gallium, caesium, and rubidium can melt on warm days, but they are normally solid under standard room conditions. Mercury is toxic, particularly through inhalation of its vapour, so spills require careful handling.