What is the X in X-mas?
rhenium rhe·ni·um (rē'nē-əm)
A rare dense metallic element with a high melting point. Atomic number 75; atomic weight 186.2; melting point 3,186°C; boiling point 5,596°C; specific gravity 21.02; valence 1, 2, 3, 4, 5, 6, 7.
A very rare, dense, silvery-white metallic element with a very high melting point. It is used to make catalysts and electrical contacts. Atomic number 75; atomic weight 186.2; melting point 3,180°C; boiling point 5,627°C; specific gravity 21.02; valence 1, 2, 3, 4, 5, 6, 7. See Periodic Table.
(Re), chemical element, very rare metal of Group VIIb of the periodic table, one of the densest elements. Predicted by the Russian chemist Dmitry Ivanovich Mendeleyev (1869) as chemically related to manganese, rhenium was discovered (1925) by the German chemists Ida and Walter Noddack and Otto Carl Berg. The metal and its alloys have found limited application as fountain pen points, high-temperature thermocouples (with platinum), catalysts, electrical contact points, and instrument-bearing points and in electrical components.