Tantalum
Isotope | Atomic mass (Da) | Isotopic abundance (amount fraction) |
---|---|---|
180Ta | 179.947 47(2) | 0.000 1176(23) |
181Ta | 180.948 00(1) | 0.999 8824(23) |
In 1969, the Commission recommended Ar(Ta) = 180.9479(3) based on new mass-spectrometric measurements, and recognized tantalum as the element whose atomic weight could be stated very precisely because of single predominant isotope, 181Ta (99.99 %). Standard atomic weight of tantalum was last revised in 2005 to Ar(Ta) = 180.947 88(2) and its isotopic composition was further revised in 2017 with no effect to the standard atomic weight.
The minor isotope, 180Ta, is radioactive with a very long half-life of more than 1013 a. It is the last quasi-stable isotope to be discovered. Interest in this isotope is further heightened by the discovery that it is not the ground-state isomer.
© IUPAC 2003
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CIAAW
Tantalum
Ar(Ta) = 180.947 88(2) since 2005
The name derives from the Greek mythological character Tantalus who was banished to Hades, the region
of lost souls where he was placed up to his chin in water, which receded whenever he tried to drink
it, and under branches of fruit, which drew back whenever he tried to pick their fruit. This name was
selected because of the insolubility of tantalum in acids; thus, when placed in the midst of acids, it is
incapable of taking any of them up. Tantalum was discovered by the Swedish chemist and mineralogist Anders-
Gustav Ekeberg in 1802.