Osmium

Osmium 190.23(3)   Os 76 1s22s22p63s23p63d104s24p6 4d105s25p64f145d66s2 [ ? ] Transition metal: Properties: Lustrous, bluish-white, extremely hard and brittle metal. Hazard: Finely divided metal is pyrophoric and may ignite spontaneously in air.

Osmium is a chemical element, having the chemical symbol Os. Its atomic number (the number of protons) is 76. It has a standard atomic weight of 190.23 g•mol ⁻¹ and is a solid in its elemental form. Osmium is extremely dense--see benchmark quantities for a comparison.

Osmium is considered a member of the "Transition metal" class of elements. At a pressure of 101.325 kPa, it has a boiling point of 5,012 °C and a melting point of 3,033 °C.