Mercury is a chemical element with the symbol Hg and atomic number 80. It is a heavy, silvery-white liquid metal that is unique among metals for being liquid at room temperature. Mercury has been used in various applications, including thermometers, barometers, and dental amalgams, due to its ability to expand and contract uniformly with temperature changes. However, mercury is also known for its toxicity. Exposure to mercury can lead to serious health issues, including neurological damage. As a result, many countries have implemented regulations to limit its use and protect public health, making awareness of its dangers crucial.