Rhenium
. Rhenium, symbol Re, rare, silvery white, metallic element. The atomic number of rhenium is 75. Rhenium is one of the transition elements of the periodic table . The existence of rhenium and the similarity of its chemical properties to those of the element manganese were predicted in 1871 by the Russian chemist Dmitry Ivanovich Mendeleyev , who named it dvi-manganese. Rhenium was discovered in 1925 by the German chemists Walter Karl Noddack and Ida Eva Tacke Noddack in the ores tantalite, wolframite , and columbite by means of X-ray spectrographic analysis, and it was later found in larger quantities in molybdenite . Rhenium metal is very hard; with the exception of tungsten , it is the least fusible of all common metals. Overall, it ranks about 79th in natural abundance among elements in crustal rocks. Rhenium melts at about 3180° C (about 5756° F), and has a specific gravity of 20.53. The atomic weight of rhenuim is 186.207. Rhenium is used in electrical filaments, welding rods,