Gold (Au). Diagram of the nuclear composition and electron configuration of an atom of gold-197 (atomic number: 79), the most common isotope of this element. The nucleus consists of 79 protons (red) and 118 neutrons (yellow). 79 electrons (white) bind to the nucleus, successively occupying available electron shells (rings). Gold is a transition metal in group 11, period 6, and the d-block of the periodic table. It has a melting point of 1064 degrees Celsius. The trends across the transition metals are due to electrons filling an inner d-subshell (here, within the 5th ring), shielding the outer electrons from the increasing nuclear charge.