How do new elements get named?
It is highly unusual for words to become the subject of avid discussion—and even of consideration by lexicographers—before they have even been coined! This is the curious situation at present in the world of science, where the announcement of four new chemical elements has created something of a stir. They can now take a permanent place in the Periodic Table of Elements, and for that they will need officially approved names. These names will have the rare distinction of being eligible for the Dictionary’s candidate list as soon as they are published. But how are their names chosen, and who makes the decision?
Filling in the Periodic Table
The Periodic Table has always had a slightly ragged bottom edge, where uranium (no. 92), originally the last known element, is followed by a gradually extending string of artificial radioactive elements with unwieldy names. These have been “discovered” in the laboratory over the past 75 years or so, synthesized by the slightly haphazard method of hurling atomic nuclei towards each other with considerable force, in the hope that they will, on rare occasions, stick together to form a larger one. In this manner, physicists have succeeded in generating all the elements of the actinide series (neptunium, 93, to lawrencium, 103) and gradually extending the sequence of superheavy elements. All of them are radioactive, undergoing nuclear decay on a timescale varying from some millions of years down to a couple of milliseconds.
The latest news concerns elements with the atomic numbers 113, 115, 117, and 118. These are of particular interest because they fill in the last remaining blanks in the bottom (seventh) row of the existing Periodic Table. In terms of their chemistry, element 117 belongs to the halogen group (with fluorine, chlorine, and iodine), and element 118 to the group of noble gases (with helium, neon, and radon). However, their extreme radioactivity means that few chemical or physical properties are ever likely to be detectable during their brief existence.
Naming and claiming
Following long historical precedent, it is generally presumed that the discoverer of a new substance is entitled to name it. However, it can be very difficult to establish whether a highly radioactive nucleus has, in fact, flashed briefly into existence during an experiment. Once the existence of transuranic elements (heavier than uranium) was accepted in theory, several early experimenters claimed to have made element no. 93 by bombarding uranium atoms with smaller nuclei, and each gave it a characteristic name with which to assert their claim of discovery, such as ‘ausonium’ (from Ausonia, a Greek name for Italy), ‘bohemium’ (referring to Bohemia), or ‘sequanium’ (from Sequana, Latin name of the river Seine). Finally, in 1940, an American team was able to confirm a successful synthesis, and called the element neptunium. (This name had in fact been used previously, in 1877, for a rare metal that turned out not to exist, and was considered again—though not used—by the discoverer of the element which came to be called germanium.)
Physicists struggle to produce new superheavy elements reliably enough to establish their existence, especially as in many cases they decay into other rare elements almost as difficult to identify, and the starting materials are also becoming progressively harder to produce. As a previous OxfordWords blog post mentioned, rival claims of discovery (and proposed names) have in the past resulted in the so-called ‘Transfermium Wars’. To help discussion of hypothetical or putative elements, IUPAC (the International Union of Pure and Applied Chemistry) introduced temporary names based on atomic numbers (symbol Z), so the new elements have been lurking in chemistry textbooks under the curious labels of ununtrium, ununpentium, ununseptium, and ununoctium, though most working scientists simply call them by their numbers.
Ununtrium (Z = 113) was produced by a Japanese research group bombarding bismuth atoms (Z = 83) with nuclei of zinc (Z = 30). This is reminiscent of the technique used by a German team in 1994 to produce darmstadtium (Z = 110) from lead (Z = 82) and nickel (Z = 28).
Ununpentium (Z = 115), ununseptium (Z = 117), and ununoctium (Z = 118) were produced by the collaboration of laboratories in Russia and the United States. In all three cases, the method used ions of an unusual heavy calcium isotope, calcium-48 (Z = 20), with the target atoms being respectively americium (Z = 95), berkelium (Z = 97), and californium (Z = 98). This technique had previously been used in 1998 to make element 114 from plutonium (Z = 94), and in 2000 to make element 116 from curium (Z = 96).
In these days of social media and internet buzz, it does not take long for someone to start a ball rolling. Fans of recently deceased celebrities, perhaps spurred on by the fashion for naming asteroids, have not been slow to propose memorializing them in the sphere of chemistry. A petition has been launched in favour of naming one of the new superheavy elements ‘lemmium’, after Ian “Lemmy” Kilmister, founder of the heavy rock band Motörhead. Another urges that element 117 should be called ‘octarine’, after the magical eighth colour of the spectrum featured in the comic fantasies of Sir Terry Pratchett. However, although scientists have been known to indulge in whimsical fancies in their terminology, it seems unlikely that we will see these—or the likes of ‘ziggium’ (after David Bowie’s alias Ziggy Stardust) or ‘severium’ (after Severus Snape, the Harry Potter character played by Alan Rickman)—appearing in the textbooks.
The IUPAC guidelines advise that “new elements can be named after a mythological concept, a mineral, a place or country, a property or a scientist”. More probable are names on the existing pattern: in May 2012, elements 116 and 118 were officially named flerovium and livermorium (from the names of research laboratories), so we are likely to see something similar, such as ‘ghiorsium’ (after American physicist Albert Ghiorso, previously proposed for element 118) or ‘moscovium’ (from Moscow, previously proposed for element 116). Once the names have been proposed, they will be checked by IUPAC’s Inorganic Chemistry Division, presented for public consideration for five months, and then officially approved by the Council of IUPAC.
The eighth row of the Periodic Table beckons. There may be particular combinations of protons and neutrons which form less volatile configurations (a little like the stable electron configurations of noble gases) somewhere in the higher reaches of atomic size, producing a so-called ‘island of stability’. Only the identification of even heavier nuclei and their half-lives and decay products will provide a test for this theory.