铽 (Tb)

发现史

发现: 1843 · Carl Gustaf Mosander

Swedish chemist Carl Gustaf Mosander discovered terbium in 1843. He detected it as an impurity in yttrium oxide, Y2O3, then known as yttria. Yttrium, erbium, and terbium are all named after the village of Ytterby in Sweden. Terbium was not isolated in pure form until the advent of ion exchange techniques. Mosander first separated yttria into three fractions, all named for the ore: yttria, erbia, and terbia. "Terbia" was originally the fraction that contained the pink color, due to the element now known as erbium. "Erbia", the oxide containing what is now known as terbium, originally was the fraction that was yellow or dark orange in solution. The insoluble oxide of this element was noted to be tinged brown, and soluble oxides after combustion were noted to be colorless. Until the advent of spectral analysis, arguments went back and forth as to whether erbia even existed. Spectral analysi

用途与应用

Terbium combines with nitrogen, carbon, sulfur, phosphorus, boron, selenium, silicon and arsenic at elevated temperatures, forming various binary compounds such as TbH2, TbH3, TbB2, TbSi2, TbN, TbP, TbS, Tb2S3, TbSe, and TbTe. In these compounds, terbium mainly exhibits the oxidation state +3, with the +2 state appearing rarely. Terbium(II) halides are obtained by annealing terbium(III) halides in presence of metallic terbium in tantalum containers. Terbium also forms the sesquichloride Tb2Cl3, which can be further reduced to terbium(I) chloride (TbCl) by annealing at 800 °C; this compound forms platelets with layered graphite-like structure. Terbium(IV) fluoride (TbF4) is the only halide that tetravalent terbium can form. It has strong oxidizing properties and is a strong fluorinating agent, emitting relatively pure atomic fluorine when heated, rather than the mixture of fluoride vapors

同位素

Naturally occurring terbium is composed of its only stable isotope, terbium-159; the element is thus mononuclidic and monoisotopic. Thirty-nine radioisotopes have been characterized from 135Tb to 174Tb. The most stable synthetic radioisotopes of terbium are 158Tb, with a half-life of 180 years, and 157Tb, with a half-life of 71 years. All of the remaining radioactive isotopes have half-lives that are less than three months, and the majority of these have half-lives that are less than half a minute. The primary decay mode before the most abundant stable isotope, 159Tb, is electron capture, which results in production of gadolinium isotopes, and the primary mode after is beta minus decay, resulting in dysprosium isotopes. It is also the heaviest element where every stable nuclide has no confirmed energetically allowed decay mode, though the heaviest element with any such isotopes is dyspro