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rhenium [Re]
From the Greek Rhenius, Rhine, a major European river. Discovered in 1925 by German chemists Walter Noaddack, Ida Noddack-Tacke & Otto C Berg.
Occurrence:
1) does NOT occur in nature as free metal
2) occurs in small amounts in the minerals gadolinite & molybdenite
3) occurs in earth's crust at 1-4 parts per billion
Characteristics:
1) obtained either as a powder or as a silver-white hard metal
2) resembles manganese
3) tarnishes slowly in moist air
4) does not react with water under normal conditions
5) annealed rhenium is very ductile
-> can be bent, coiled & rolled
6) rhenium dust can burn or explode
7) natural rhenium is a mixture of one stable & one radioactive isotope with a long 1/2 life
-> 28 stable isotopes known
Uses:
1) catalysts
a) resistant to poisoning from nitrogen, sulfur & phosphorous
b) hydrogenation
c) hydrocracking
d) reforming & disproportionation of alkenes
2) thermocouples
3) filaments for mass spectrometers
4) thermistors
5) tungsten & molybdenum-based alloys
6) photoflash lamps
7) electrical contact material
Related
periodic table
General
chemical element
metal
Properties
SIZE: AW = 186.21
atomic number
VALUE: 75
VALENCE: XE 4F14 5D5 6S2
References
- Webster's Ninth New Collegiate Dictionary, Miriam-
Webster Inc. Springfield, MA 1990
- Chemical & Engineering News, Sept 8, 2003