How Elements Get Their Names

Element 117 existed for six and a half years before it was allowed a name. From the announcement of its synthesis in April 2010 until IUPAC ratified tennessine in November 2016 its official designation was ununseptium — not a joke name, but Latin one-one-seven with an ending stuck on.

A stand-in name of that kind exists because naming is the last step, not the first, and the gap between making an atom and being allowed to call it something can run for years. The rules governing what happens in that gap are more specific than most people assume.

Five things an element may be named after, and nothing else

IUPAC's recommendations — issued in 2002 and revised in 2016 — restrict a new element's name to one of five sources:

• a mythological concept or character, which by convention includes astronomical objects
• a mineral or similar substance
• a place or geographical region
• a property of the element
• a scientist

That is the complete list. There is no category for a sponsor, an institution as such, an event or an abstract virtue, and the restriction is enforced. It also lands slightly awkwardly on the modern practice of naming elements after the laboratory that made them, which is handled by naming the town instead — darmstadtium for Darmstadt, dubnium for Dubna, hassium for the German state of Hesse.

The last two letters are not the discoverer's choice

The 2016 revision added a rule that the discoverers cannot negotiate: the ending has to match the column. Elements in groups 1 to 16, the f-block included, take -ium. Group 17 takes -ine, matching fluorine, chlorine, bromine and iodine. Group 18 takes -on, matching neon, argon, krypton, xenon and radon.

This is why the two 2016 names at the right-hand end of the table look different from the other two. Nihonium and moscovium are in group 13 and 15 and end conventionally. Tennessine is in group 17 and had to end in -ine. Oganesson closes group 18 and had to end in -on. Neither element has ever had its chemistry measured — nobody knows whether tennessine behaves like a halogen or oganesson like a noble gas — so the suffixes encode a position on a chart rather than an observed property. Helium is the standing reminder that the convention is imperfect: it ends in -ium because it was named for the Sun before anyone knew it was a gas that would not react with anything.

The name comes last, and slowly

Nothing gets named until the discovery itself is accepted. A claim goes to a Joint Working Party convened by IUPAC and IUPAP, which examines the evidence — usually a handful of atoms identified by their decay chain — and decides whether priority has been established and to whom. That assessment can take years and, where two laboratories claim the same element, can end in shared credit.

Only then are the accepted discoverers invited to propose a name and a two-letter symbol. The proposal goes to IUPAC's Inorganic Chemistry Division, and if it survives that, it is published for a five-month public review before the IUPAC Council votes. The consultation is genuine rather than ceremonial: it exists because a name, once ratified, is effectively permanent, and because objections tend to come from people who were not in the room.

In the meantime the element carries a systematic name built straight from its atomic number, using a set of numeric roots — nil, un, bi, tri, quad, pent, hex, sept, oct, enn — strung together and finished with -ium. Element 118 was ununoctium, symbol Uuo, for a decade before it became oganesson. Element 119, which nobody has yet made, is ununennium if you need to refer to it.

What the existing 118 are actually named after

Run the whole table through those five categories and the distribution is lopsided in a way that tracks the history of who was doing chemistry, and where.

Places dominate, with well over thirty. Four of them — yttrium, terbium, erbium and ytterbium — come from one Swedish village, and holmium and thulium were named nearby in spirit, for Stockholm and for the mythical northern land of Thule. Lutetium is Paris, hafnium is Copenhagen, ruthenium is Russia, polonium is Poland — chosen by Marie Curie as a political act, for a country that did not exist on the map at the time.

Properties, mostly Greek and mostly about colour or smell, account for a large second group. Chlorine is pale green, iodine violet, rhodium rose, cesium sky blue, rubidium deep red, indium indigo — the last three all named for the colour of a spectral line rather than of the substance. Bromine and osmium are both named for their smell. Argon means idle and krypton means hidden, which is a fair description of a noble gas from the point of view of the person trying to find it. Dysprosium means "hard to get at", and its discoverer meant it.

Mythology supplies titanium, vanadium after the Norse Vanadís, thorium, promethium, and the matched pair of niobium and tantalum — Tantalus and his daughter Niobe, named that way because the two elements are so alike and so hard to separate that the mythological relationship was the clearest way to say so.

Scientists are a recent phenomenon, and which of them came first is genuinely argued about. Two nineteenth-century names reach a person through a mineral rather than directly — samarium and gadolinium, both christened by Paul-Émile Lecoq de Boisbaudran, in 1879 and 1886 respectively. Date order hands the title to samarium and most reference works award it on that basis. Insist instead that an element be named for its honorand with no rock in between, and the answer jumps to curium in 1944.

Everything else here is twentieth-century and clustered in the actinides and beyond: einsteinium, fermium, mendelevium, nobelium, lawrencium, rutherfordium, seaborgium, bohrium, meitnerium, roentgenium, copernicium, flerovium, oganesson. Exactly two honour someone who was alive to read the announcement — Glenn Seaborg, over objections, and Yuri Oganessian.

The names that no longer match their symbols

Eleven elements carry a symbol that does not correspond to their English name, and every one of them is a fossil of an older name that lost.

Sodium is Na from natrium, potassium is K from kalium, iron is Fe from ferrum, copper is Cu from cuprum, silver is Ag from argentum, tin is Sn from stannum, antimony is Sb from stibium, gold is Au from aurum, mercury is Hg from hydrargyrum, lead is Pb from plumbum, and tungsten is W from wolfram. Ten Latin, one German. In each case the symbol was fixed by Berzelius in the early nineteenth century from the scholarly name, while the vernacular English word carried on regardless.

Which is a reminder that the tidy five-category rulebook governs only the elements named since there was an authority to write one. Most of the table was named before anybody was asking permission — and a good number of those names were fought over for decades before they stuck.