Palladium (Pd). Diagram of the nuclear composition, electron configuration, chemical data, and valence orbitals of an atom of palladium-106 (atomic number: 46), the most common isotope of this element. The nucleus consists of 46 protons (red) and 60 neutrons (orange). 46 electrons (white) successively occupy available electron shells (rings). Palladium is a transition metal in group 10, period 5, and the d-block of the periodic table. It has a melting point of 1555 degrees Celsius. The transition metal trends are due to electrons filling an inner d-subshell (here, within the 4th ring), shielding the outer (valence) electrons from the increasing nuclear charge. Diagram of palladium atomic composition. Naturally occurring palladium is composed of seven isotopes, which includes six stable isotopes. The most stable radioisotope is Pd-107 with a half-life of 6.5 million years. However, the mos abundant is Pd-106 (27.33
