Caption

Copper (Cu). Diagram of the nuclear composition and electron configuration of an atom of copper-63 (atomic number: 29), the most common isotope of this element. The nucleus consists of 29 protons (red) and 34 neutrons (blue). Copper is a transition metal in group 11, period 4, and the d-block of the periodic table. It has a melting point of 1084 degrees Celsius. The trends across the transition metals are due to electrons filling an inner d-subshell (here, within the 3rd ring), shielding the outer electrons from the increasing nuclear charge.