Mercury Mercury’s symbol is Hg, its atomic number is 80, its atomic mass is 200.59, its in group 12 and in period 6, and it also has two valence electrons. Its standard state is liquid at 298ēK and it is the heaviest known elemental liquid. It has a silvery white color. It is named after the planet "Mercury" the origin of the symbol Hg is the Latin word "hydrargyrum" meaning "liquid silver". Mercury was known to ancient Chinese and Hindus before 2000 B.C. and was found in tubes in Egyptian tombs dated from 1500 B.C. Mercury is the only metal liquid at ordinary temperatures. Mercury is sometimes called quicksilver. It sometimes occurs free in nature a