Explanation:
Mercury is the only common metal that exists in liquid form at normal room temperature. Its chemical symbol is Hg, derived from the Latin name Hydrargyrum, meaning liquid silver. Mercury has unusual physical properties compared to most metals. It has a relatively low melting point of about −39 degrees Celsius, which allows it to remain liquid under ordinary environmental conditions. Because mercury expands and contracts uniformly with temperature changes, it was historically used in thermometers and barometers for measuring temperature and atmospheric pressure. The shiny silver appearance of liquid mercury and its high density also make it distinctive among elements. However, mercury is a toxic substance and prolonged exposure can damage the nervous system, kidneys, and other organs. For this reason, the use of mercury in household thermometers and medical instruments has been reduced and replaced by safer alternatives such as alcohol thermometers or digital sensors. Despite these concerns, mercury remains an important element in chemistry and environmental science studies. Questions about mercury being the only metal that is liquid at room temperature are frequently asked in general science sections of competitive examinations.