Mercury was known before 2000 B. C. to ancient Chinese and Hindus. It has also been found in Egyptian tombs. This element was named after the planet Mercury. Its symbol, Hg, came from the Latin word "hydrargyrum", which means liquid silver.

At ordinary temperatures, mercury is a shiny, mobile liquid. Silver in color and with no odor, it is the heaviest known elemental liquid. Mercury does not occur freely in nature; it is found mainly in cinnabar ore.

Mercury has been used in many products: batteries, thermometers, thermostats, barometers, diffusion pumps, mercury-vapor lamps and advertising signs, dental amalgams and pesticides. It has the ability to alloy with most metals, is liquid at room temperature, easily vaporizes and freezes, and conducts electricity. But mercury's health effects on living things outweigh industry's need for it. Replacements for mercury are being used whenever possible.