Mercury is a naturally-occurring chemical element found in rock in the earth's crust, including in deposits of coal. On the periodic table, it has the symbol "Hg" and its atomic number is 80. It exists in several forms: Elemental (metallic) mercury.
Mercury as a metal is used for extraction of gold and silver, as a catalyst for chlor-alkali production, in manometers for measuring and controlling pressure, in thermometers, in electrical and electronic switches, in fluorescent lamps, and in dental amalgam fillings.
Mercury (Hg) is an element called a transition metal and is the only metal found as a liquid at room temperature. It is very heavy and dense. Mercury is extremely poisonous, with many people becoming very sick after being exposed.
Mercury's distinctive properties have captivated humans for centuries. Early evidence of its use dates back to 1500 BC, with civilizations around the world employing it in various ways. The ancient Egyptians and Chinese used mercury for medicinal purposes, often with harmful consequences due to its toxicity.
Alchemists in the medieval period were particularly fascinated by mercury, believing it held the key to immortality and the creation of gold. They named it after the Roman god Mercury, associated with swiftness and fluidity, due to the element's liquid state at room temperature.
Osmium occurs uncombined in nature and also in the mineral osmiridium (an alloy with iridium). Most osmium is obtained commercially from the wastes of nickel refining.