Rhenium is a metal element that is denoted by the atomic symbol, Re. Its atomic weight is 186.207, and its atomic number is 75. It is a black to silver-grey material that is typically used in a powder form. The element is relatively abundant in nature, occurring to the extent of about 0.001 parts per million in the Earth's crust. Its melting point is 5,766.8°F (3,186°C), and its boiling point is estimated to be 10,104.8°F (5,596°C). Its specific gravity is 21.02, greater than all but three other elements.

The discovery of rhenium was not made until the 1900's. By 1920, only a handful of elements remained to be discovered. Henry Moseley 's discovery of atomic numbers in 1914 revealed only seven empty spaces in the periodic table, numbers 43, 61, 72, 75, 85, 87, and 91. The search for elements 43 (eka-manganese) and 75 (dwi-manganese) apparently ended in June 1925 when Walter Noddack (1893-1960), Ida Tacke, and Otto Berg announced...