Unununium

How did UNUNUNIUM make it onto my Cool Words list? The story of this word begins with a thing chemists call the Actinide Series. Actually, the real story begins with the Transactinide Series, but there's no point telling a child a story about a transoceanic voyage if they've never heard of an ocean. So …

The Actinide Series is a sequence of chemical elements starting at Actinium (atomic number 89) and ending with Lawrencium (atomic number 103), including all the atomic numbers in between. A generic element in this series is referred to as an ACTINIDE, or an ACTINOID (so, yes, the plurals are good too).

Here is the full Actinide Series, ordered by increasing atomic number, with official chemical symbols enclosed in parentheses:

89 ACTINIUM (Ac)
90 THORIUM (Th)
91 PROTACTINIUM (Pa)
92 URANIUM (U)
93 NEPTUNIUM (Np)
94 PLUTONIUM (Pu)
95 AMERICIUM (Am)
96 CURIUM (Cm)
97 BERKELIUM (Bk)
98 CALIFORNIUM (Cf)
99 EINSTEINIUM (Es)
100 FERMIUM (Fm)
101 MENDELEVIUM (Md)
102 NOBELIUM (No)
103 LAWRENCIUM (Lr)

Of course, the Scrabbler's Actinide Series is considerably shorter:

ACTINIDE
CTENIDIA
DIACTINE
INDICATE

As the name suggests, the TRANSACTINIDE series begins where the actinide series ends. This series doesn't have a well-defined endpoint, but I'll end the list with the heaviest element that has so far been officially recognised and named:

104 RUTHERFORDIUM (Rf)
105 DUBNIUM (Db)
106 SEABORGIUM (Sg)
107 BOHRIUM (Bh)
108 HASSIUM (Hs)
109 MEITNERIUM (Mt)
110 *DARMSTADTIUM (Ds)
111 *ROENTGENIUM (Rg)

Note: If you're hoping I can explain why elements 110 and 111 are not allowed in Scrabble, with so many other proper nouns being perfectly acceptable, I'm afraid I'm going to disappoint you. Maybe they just haven't been doing the rounds for long enough yet.

What's so special about the transactinide series? The elements of this series have a number of important chemical properties, but I want to focus on something much more interesting and less important: The Element Naming Controversy. You won't learn much chemistry in this story, but you'll learn some cool Scrabble words.

As far as we know, none of the transactinides occur in nature (largely due to their short half-lives; that is, they disintegrate very quickly), so all the known transactinides have been synthesized in laboratories. From about the 1950s, laboratories were set up specifically to synthesize new elements, and the competition to be the first to succeed became intense. The main competitors in this race were laboratories based in Berkeley (America), Dubna (Russia), and Darmstadt (Germany). It was the chemists answer to the great space race. Controversy erupted in the 1960s when two laboratories both claimed to have created elements 104 and 105. The problem was not just one of priority of discovery. The question of naming new elements also became a source of fierce contention. To appreciate the importance of an element's name, you need only imagine the response of the Americans if a German laboratory had decided to call a new element *Hitlerium. They didn't of course, but you get my point, right? Some sort of international process had to be worked out. And so, eventually, it was.

The International Union of Pure and Applied Chemistry (IUPAC), together with another physics body, set up an internationally agreed process by which discoveries of new elements could be confirmed and assigned official names, which would then be recognised throughout the world. I found the whole process behind validating the discovery of something invisible really fascinating, but I realise you're obsessed with Scrabble, so I'll do my best to stick to the subject of naming.

IUPAC decided that once they were satisfied that an element had indeed been discovered, the research team who discovered it could also come up with a name. At least, that's how the research teams saw it. In fact, IUPAC were very careful to point out that although "discoverers have the right to suggest a name to IUPAC", only the IUPAC itself can declare the official name. But in practice, they usually accepted the discoverer's suggestion, provided it satisfied certain criteria, like these:

1. To keep with tradition, the new element should be named after:

- a mythological concept or character
- a mineral, or similar substance
- a place or geographical region
- a property of the element
- a scientist

2. For linguistic consistency, the new element should end in -ium

3. To avoid confusion, "when a name has been in unofficial use for a particular element, but a different name is ultimately chosen for that element, then the first name cannot be transferred for use for another element".

The last criterion can be illustrated with the case of element 105. This element was called Hahnium extensively in the literature, before it was officially named Dubnium. So Hahnium is not allowed to be used for any subsequently discovered element. Ever! Poor old Otto Hahn. Oh well – I'd prefer to have a beer than an element named after me anyway. And besides, he still gets to see his name on the Scrabble board, because Collins says: HAHNIUM is good.

Clarifying the process of official names isn't the end of it though. Scientists still need to be able to refer to a hypothetical element before it is discovered, or before it is assigned an official name. Without this process, scientists would start using names anyway, and then these would have to be erased from the collective memory of a whole generation. Indeed, this is just what happened to the early transactinides. Element 104, for example, was referred to by different names, by competing laboratories, for nearly three decades: Rutherfordium by the Americans, and Kurchatovium by the Russians. Rutherfordium won the day, but you'll still find KURCHATOVIUM in CSW, even though you won't find it in the official Periodic Table.

To address this issue, IUPAC introduced a naming scheme that could be used to assign temporary systematic names to the transactinides until things were settled. The recipe for temporarily naming a newly discovered, or hypothetical, element is very simple, and is based on the element's atomic number. Firstly, each digit in the atomic number is replaced by one of the following prefixes:

0 nil- (n)
1 un- (u)
2 bi- (b)
3 tri- (t)
4 quad- (q)
5 pent- (p)
6 hex- (h)
7 sept- (s)
8 oct- (o)
9 enn- (e)
10 deca- (d)

Note: The purist might well recoil here at the seemingly indiscriminate mix of Greek and Latin prefixes. (The non-purist should be ashamed of themselves for not even noticing!) Don't panic. The mix is intentional, and is designed to ensure that each digit is represented by a distinct letter. These guys weren't lexicographers – they were scientists – so it was all well thought out.

Secondly, the name of the element is formed by simply concatenating these prefixes, and then tagging the traditional –ium on the end. Below is the resulting list of systematic names for all transactinides whose discovery has been reported at the time of writing (although those beyond 111 have not yet been ratified by IUPAC):

104 UNNILQUADIUM (Unq)
105 UNNILPENTIUM (Unp)
106 UNNILHEXIUM (Unh)
107 UNNILSEPTIUM (Uns)
108 *UNNILOCTIUM (Uno)
109 *UNNILENNIUM (Une)
110 *UNUNNILIUM (Unn)
111 UNUNUNIUM (Uuu)
112 UNUNBIUM (Uub)
113 *UNUNTRIUM (Uut)
114 *UNUNQUADIUM (Uuq)
115 *UNUNPENTIUM (Uup)
116 *UNUNHEXIUM (Uuh)
118 *UNUNOCTIUM (Uuo)

Note: Well, ok, I left out step one-and-a-half. To avoid the awkward `ii' combination, one `i' gets omitted whenever this happens. So we get Ununbium rather than *Ununbiium, for example. Also, whenever the sequence -90- occurs, we avoid the `nnn' combination (from `enn + nil') by deleting an `n'.

Again, don't ask me for the recipe Collins used in deciding which ones are in, and which ones are out. Although I suspect it may have involved a dart and one or two cartons of Hahns.

Now, if you haven't done so already, take a look at element number `111'. Suddenly, Unununium doesn't look so ridiculous any more, does it? (Well, ok, it's not the prettiest thing to pronounce – but that was never the intention of the scheme.) In fact, you probably want to know more about it, right? Unfortunately, there isn't much to say, but let me tell you what I've been able to find out.

Unununium was discovered (well, synthesized) by a team of nuclear chemists led by one S. Hofmann in 1995 in Darmstadt (Germany). But it wasn't until 2003 that their discovery was finally ratified, and then they had to wait until 1 November 2004 before their proposed name of *Roentgenium (Rg) was officially accepted, thereby outdating the temporary placeholder that triggered my interest in this story in the first place. And why did Hofmann's team choose this name? The choice was explained in an official press release:

"Wilhelm Conrad Roentgen discovered X-rays on 8 November 1895, a new type of rays to which he gave this name in view of their uncertain nature. Their use has subsequently revolutionized medicine, found wide application in technology and heralded the age of modern physics, which is based on atomic and nuclear properties. In 1901, six years after their discovery, the benefit of X-rays to mankind was so evident that Roentgen was awarded the first Nobel Prize in Physics. Element 111 was synthesized exactly 100 years after Roentgen's discovery. To honor Wilhelm Conrad Roentgen, the name, roentgenium, was proposed for the element with atomic number 111."

Although *Roentgenium didn't pass muster with Collins, you'll find plenty of valid words derived from this great scientist's name. ROENTGEN, and its variant RONTGEN, for starters!

In fact, Hofmann has a number of new elements under his belt, but they are still patiently awaiting approval, so we don't know what he plans to call them yet.

To add at least a smidgen of chemistry to the discussion, I'll just casually mention that Hofmann's team produced Unununium by bombarding a Bismuth target with a beam of Nickel, in a process called `fusion' that is very popular among *transactinidians (a word which is so long that it wouldn't be allowed even if it was). Like most transactinides, only a handful of atoms could be produced from the process, and even these atoms are `inferred', rather than `seen', from the results of very complex data analyses.

Since you can't produce jars of the stuff, you can't really say much about its properties. So if you look up the official details of this element you'll see entries like this:

Colour: Unknown
Boiling Point: Unknown
Hobbies: Unknown

and so forth; culminating in:

Applications: No known uses.

No known uses? Obviously our esteemed chemists have never heard of a U-dump!

So there you have it: the story behind, the otherwise ridiculous, UNUNUNIUM. And you got about another 50 words for free!

Before leaving, I should mention something about pronunciation. The prefix UN- is actually pronounced `yoon' (as in `moon'). So if you come up to me in the street and refer to this word, pronouncing the UNs to rhyme with `guns', I'll know you don't read my articles all the way to the end ;-)

References

Naming of new elements, Pure Appl. Chem. 74(5), pp. 787-791, 2002
Naming of elements 110 and beyond, Chem. Int. 2002, 24(2), p. 7
On the claims for discovery of elements 110, 111, 112, 114, 116, and 118 Pure Appl. Chem. 75(10), 1601-1611, 2003
Name and symbol of element of atomic number 110, Pure Appl. Chem. 75(10), 1613-1615, 2003
Name and symbol of the element with atomic number 111, Pure Appl. Chem. 76(12), 2101-2103, 2004
On the discovery of the elements 110-112, Pure Appl. Chem. 73(6), pp. 959-967, 2001
Names and symbols of transfermium elements, Pure Appl. Chem. 69(12), pp. 2471-2473, 1997
Criteria that must be satified for the discovery of the new chemical element to be recognized, Pure Appl. Chem., 63(6), pp. 879-886, 1991

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