A chemical element, Au, atomic number 79 and atomic weight 196.967, a deep yellow, soft, and very dense metal. Gold is classed as a heavy metal and as a noble metal; commercially, it is the most familiar of the precious metals. Copper, silver, and gold are in the same group of the periodic table of elements. The Latin name for gold, aurum (glowing dawn), is the source of the chemical symbol Au. There is only one stable isotope of gold, that of mass number 197.