Dark gray, dense metal which can take on a high polish m.p. 2227±20 ºC; 4041±36 ºF b.p. 4602 ºC; 8316 ºF density 13.31 g/cc; 830.92 pound/cubic foot	memory peg
	1922 Dirk Coster & György Karl von Hevesy, Denmark
	Hafnia = København (Copenhagen) (Latin)

Chemists suspected long time, that Zirconium minerals contained the impurity of some unknown element. Many of them reported the discovery of this element:

• 1845: The Swedish chemist and mineralogist Lars Fredrik Svanberg (1805-1878) reported the discovery in zircon of this new element, which he named Norium.
• Ostranium (остраний),
• 1869: Henry Clifton Sorby discovered Jargonium by spectroscopical analysis. He retracted his claim the following year: the spectrum he had seen was due to impure Zirconium (note).
• 1879: Tellef Dahl, inspector of the Norwegian mines, found a new metal in nickel pyrite of Kragerø, in Norway, and named it Norwegium (Ng) (norvégium) after the country in which it was first found (note).
• 1911: Nigrium.
• Euxenium (эвксений).

On the basis of the periodic law the Danish chemist Julius Thomsen (1826-1909) showed in 1895 that an element must exist between the rare earths and Tantalum, different from the rare earths and close to Zirconium.

The final discovery of Hafnium in the first half of the twentieth century was one of chemistry’s more controversial episodes. In 1911 Georges Urbain, the French chemist and authority on the rare earths, claimed to have isolated the element of atomic number 72 from a sample of rare-earth residues, and named it Celtium (Ct) (note). It seems very unlikely that this element could have been found in the necessary concentrations along with rare earths. But, in 1922 Urbain and Alexandre Dauvillier claimed to have X-ray evidence to support the discovery (note).

Around the same time a mineral orthite, found on the Svjatoj Nos peninsula in the Trans-Baykal region, was brought under the attention of the chemists in St. Petersburg. It was supposed that orthite contained one of the most interesting radioactive elements, Thorium. The geochemist Vladimir Ivanovich Vernadskij (Владимир Иванович Вернадский) (1863-1945) charged the analysis of orthite to his student Konstantin Avtonomovich Nenadkevich (Константин Автономович Ненадкевич) (1880-1963). Soon he extracted from orthite the assumed thorium, but they were not confident, that they had isolated Thorium. Nenadkevich determined the atomic weight of the element and it turned out that it was equal to 178, while the atomic weight of Thorium is 232. In accordance with the periodic law the element in orthite must be found in Mendeleyev's table between Lutecium and Tantalum, thus element #72. Since this was an empty place, Nenadkevich had found a new element, which he named Asium (азием), after Asia, where the mineral was found. Because of the First World War and the following Civil War in Russia, the necessary further confirmation research and publication was delayed.

By that time Niels Bohr had developed his atomic theory and so was confident that element 72 would be a member of Group 4 and was more likely to be found along with zirconium than with the rare earths. Working in Bohr's laboratory in Copenhagen in 1922, the Dutchman Dirk Coster (1889-1950) and the Hungarian György Karl von Hevesy (1885-1966) used X-ray spectroscopic analysis to show that element 72 was present in Norwegian zircon.

In November 1922 was announced that the Nobel Prize in Physics for the year 1922 was awarded to Bohr "for his services in the investigation of the structure of atoms and of the radiation emanating from them". Bohr went to Stockholm to receive the prize and would give his Nobel Lecture "The structure of the atom". The day before his presentation, Bohr received a very significant message of Coster and Hevesy which had remained in Copenhagen. They had just highlighted lines which must be from element 72. The Dutchman Coster proposed the name Hafnium (after Copenhagen), and although Bohr preferred the name Danium (after Denmark), he accepted Coster's name. Bohr announced the discovery of Hafnium in his Nobel Lecture:

"In these circumstances Dr. Coster and Prof. Hevesy, who are both for the time working in Copenhagen, took up a short time ago the problem of testing a preparation of zircon-bearing minerals by X-ray spectroscopic analysis. These investigators have been able to establish the existence in the minerals investigated of appreciable quantities of an element with atomic number 72, the chemical properties of which show a great similarity to those of zirconium and a decided difference from those of the rare-earths.*" (note)

The note in the published version says:

"* For the result of the continued work of Coster and Hevesy with the new element, for which they have proposed the name hafnium, the reader may be referred to their letters in Nature of January 20, February 10 and 24, and April 7."

The element is named after Hafnia, the Latin name of Copenhagen, capital of Denmark, the town the element was discovered. Copenhagen, or more correct in Danish København, means literally "merchant's harbour".

Further reading:

• Mary Elvira Weeks, Discovery of the Elements, comp. rev. by Heny M. Leicester (Easton, Pa.: Journal of Chemical Education, 1968), pp. 820-823.
• François Gaudreau, Le tableau périodique et la découverte de l'hafnium. Sherbrooke, Québec (on-line)
• Eric Scerri, "Prediction of the Nature of Hafnium from Chemistry, Bohr's Theory and Quantum Theory." Annals of Science 51 (1994): 137-150. (on-line)