Element Terbium, Tb, Lanthanide

Terbium also known as ionium, and incognitum.

The existence of this element was many times put in a doubt within half of century despite it was discovered by such rare earths guru as Carl Gustaf Mosander who in 1843 had separated yttria into three earths, a colorless oxide which kept the name yttria; a yellow earth erbia, and a rosy earth terbia, containing the elements yttrium, terbium, and erbium. However eve such recognized scientists as Robert Wilhelm Bunsen and Per Teodor Cleve had recovered only two oxides and found doubtful the existence of the third one - the terbia earth. Later Lecoq de Boisbaudran found terbium in pseudo element named mosandrium. However he then became confused supposing that a while series of terbines were discovered. Only at the beginning of 20th century French scientist Georges Urbain recovered pure terbium and solved this issue.

Lanthanide Terbium crustal abundance is 4.3x10^-4 mass %; in sea water 10^-7 mg/L; as other rare earth elements it is contained in many minerals, including cerite, gadolinite, monazite, xenotime, loparite and euxenite.

Terbium is extracted from the rare earth elements mixture by extraction methods and chromatography. Terbium metal is metallothermically reduced from TbCl₃ or TbF₃.