Pelopium was the proposed name for a new element found by the chemist

Heinrich Rose Heinrich Rose (6 August 1795 – 27 January 1864) was a German mineralogist and analytical chemist. He was the brother of the mineralogist Gustav Rose and a son of Valentin Rose. Rose's early works on phosphorescence were noted in the Quarte ...

in 1845. The name derived from the Greek king and later god

Pelops In Greek mythology, Pelops (; ) was king of Pisa in the Peloponnesus region (, lit. "Pelops' Island"). He was the son of Tantalus and the father of Atreus. He was venerated at Olympia, where his cult developed into the founding myth of the O ...

, son of Tantalus. During the analysis of the mineral

tantalite The mineral group tantalite Fe,_manganese.html"_;"title="iron.html"_;"title="iron">Fe,_manganese">Mn)Tantalum">Ta2oxygen.html" ;"title="manganese">Mn)Tantalum.html" ;"title="iron">Fe,_manganese.html" ;"title="iron.html" ;"title="iron">Fe, mang ...

he concluded that it does contain an element similar to

niobium Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has s ...

and

tantalum Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as ''tantalium'', it is named after Tantalus, a villain in Greek mythology. Tantalum is a very hard, ductile, lustrous, blue-gray transition metal that ...

. The similar reactivity of niobium and tantalum complicated preparation of pure samples and therefore several new elements were proposed, which were later found to be mixtures of niobium and tantalum. The differences between tantalum and niobium and the fact that no other similar element was present were unequivocally demonstrated in 1864 by

Christian Wilhelm Blomstrand Christian Wilhelm Blomstrand (20 October 1826 – 5 November 1897) was a Swedish mineralogist and chemist. He was a professor at the University of Lund from 1862-1895, where he isolated the element niobium in 1864. He developed an early version ...

, and

Henri Etienne Sainte-Claire Deville Henri is an Estonian, Finnish, French, German and Luxembourgish form of the masculine given name Henry. People with this given name ; French noblemen :'' See the ' List of rulers named Henry' for Kings of France named Henri.'' * Henri I de Mon ...

, as well as Louis J. Troost, who determined the formulas of some of the compounds in 1865 and finally by the Swiss chemist Jean Charles Galissard de Marignac. This confusion arose from the minimal observed differences between tantalum and niobium. Both tantalum and niobium react with

chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...

and traces of oxygen, including atmospheric concentrations, with niobium forming two compounds: the white volatile

niobium pentachloride Niobium(V) chloride, also known as niobium pentachloride, is a yellow crystalline solid. It hydrolyzes in air, and samples are often contaminated with small amounts of NbOCl3. It is often used as a precursor to other compounds of niobium. NbCl ...

(NbCl₅) and the non-volatile

niobium oxychloride Niobium oxychloride is the inorganic compound with the formula NbOCl3. It is a white, crystalline, diamagnetic solid. It is often found as an impurity in samples of niobium pentachloride, a common reagent in niobium chemistry. Structure In the s ...

(NbOCl₃). The claimed new elements ''pelopium'', '' ilmenium'' and ''

dianium Dianium was the proposed name for a new element found by the mineralogist and poet Wolfgang Franz von Kobell in 1860. The name derived from the Roman goddess Diana. During the analysis of the mineral tantalite and niobite he concluded that it do ...

'' were in fact identical to niobium or mixtures of niobium and tantalum.

References

{{reflist Misidentified chemical elements Niobium Tantalum