1 × 2 × 3 cm chunk of hafnium
29 September 2023
Hafnium is a lustrous, silvery metal found in many zirconium ores. It has atomic number 72 and the symbol Hf. Its primary use is in the control rods of nuclear reactors, but it is also used in the manufacture of microprocessors.
The existence of hafnium was predicted in 1871 by Mendeleev’s periodic table, but the element was not discovered until Dirk Coster and George de Hevesy of Copenhagen’s Universitets Institut for Teoretisk Fysik identified it in 1922. Its existence was announced by Niels Bohr, Coster and Hevesy’s supervisor in the lab, in his 11 December 1922 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.
But the name hafnium was not proposed until Coster and Hevesy did so a few weeks later in a 20 January 1923 letter in the journal Nature:
For the new element we propose the name Hafnium (Hafniae = Copenhagen).
Hafnia is a modern Latin name for Copenhagen, a combination of the Danish havn (harbor) + the Latin suffix -ium.
The search for Mendeleev’s predicted element #72 kicked off a rather fierce debate in chemical circles, with many scientists scrambling to be the first to identify it. In 1911, Georges Urbain claimed to have identified the missing element, which he named celtium:
During repeated fractionation of the nitrates in the isolation of lutecium from gadolinite earths, a few drops of a mother liquor were obtained that did not crystallise. This contained a new oxide belonging to the rare earths and characterised by a magnetic susceptibility three or four times less than that of lutecia. The name celtium is given to the corresponding element, and the symbol Ct assigned to it.
Urbain’s supposed discovery was eventually proven incorrect, but not after considerable debate and in-fighting. This particular debate over the discovery of an element was especially significant because it marked a shift in methodology. Urbain had used traditional chemical methods in his search for the element, while Coster and Hevesy had used the new technique of x-ray spectroscopy, and their discovery marked a shift in elemental research away from chemistry and toward physics. Hafnium turned out to be the second-to-last stable element to be discovered.
Sources:
Bohr, Niels. “The Structure of the Atom” (Nobel lecture), 11 December 1922, 42. Nobelprize.org.
Coster, D. and G. Hevesy. “On the Missing Element of Atomic Number 72” (2 January 1923). Nature, 111, 20 January 1923, 79/2. DOI: 10.1038/111079a0.
Fernelius, W. Conard. “Hafnium.” Journal of Chemical Education, 59.3, 1 March 1982, 242. DOI: 10.1021/ed059p242.
Oxford English Dictionary, second edition, 1989, hafnium, n.; third edition, March 2022, celtium, n.
Scerri, Eric. A Tale of Seven Scientists and a New Philosophy of Science. Oxford: Oxford UP, 2016, 208–209. ProQuest Ebook Central.
Urbain, Georges. “A New Element Accompanying Lutecium and Scandium in Gadolinite Earths: Celtium.” Journal of the Chemical Society, 100.2, 1911, 115. Archive.org.
Photo credit: Chemical Elements: A Virtual Museum, 2009. Wikimedia Commons. Licensed under a Creative Commons Attribution 3.0 Unported License.