Hg. Mercury in its elemental (pure) form, that is, as a metal; hence the synonym metallic mercury. A shiny, silver-gray metal that is a liquid at room temperature.

Metallic (elemental) mercury has many uses and examples where it is found are thermometers, barometers, dental amalgams, batteries, fluorescent lights and some electrical switches. It is rarely found in nature.

For more information on elemental mercury see :
Web Elements properties for Mercury