Chemistry in its element: flerovium

Since this podcast was first published, the name of this element has been ratified as flerovium (symbol Fl) by the International Union of Pure and Applied Chemistry (Iupac). The name recognises Russian physicist Georgiy Flerov, who discovered the spontaneous fission of uranium. Flerov also gives his name to the laboratory at the Joint Institute for Nuclear Research in Dubna, Russia, where the element was first made.


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Meera Senthilingam

This week we are element spotting with Brian Clegg.

Brian Clegg

It's easy to accuse the scientists who produce new, very heavy elements of being chemistry's train spotters. Just as train spotters spend hours watching for a particular locomotive so they can underline it in their book, it may seem that these chemists laboriously produce an atom or two of a superheavy element as an exercise in ticking the box. But element 114 has provided more than one surprise, showing why such elements are well worth investigating.

This is one of the elements that is still waiting to have a proper name assigned to it, so it remains for the moment ununquadium (just one-one-four-ium in truncated Latin), with the symbol Uuq, until it receives a more aesthetically pleasing label.

Element 114 sits in an island of stability, a position in the periodic table where a spherical nuclear configuration suggests that half lives should be relatively long. That word 'relatively' is important. Where, for instance, darmstadtium, which precedes the island of stability, has a typical half life measured in microseconds, element 114's isotope with atomic mass 289 stays around for seconds at a time.

In principle, there is an isotope of element 114 that should do even better. The expectation, long before 114 was even produced, was that ununquadium 298 should be particularly stable. The nucleus of this isotope would have 114 protons and 184 neutrons, which should provide complete energy levels in the nucleus and hence unusual stability. Ununquadium 298 has a predicted half life that could reach into thousands of years - remarkable for the transfermium elements, which are generally the mayflies of the periodic table.

To date we haven't been able to test this thesis, because no isotope 298 has been produced. The first sighting of element 114 was in 1998 at the Joint Institute for Nuclear Research at Dubna in Russia. This doesn't mean that we can look forward to dubnium as a name for the element, this is already assigned to element 105.

Using a plutonium 244 target, produced by Kenton Moody at the Lawrence Livermore National Laboratory in California, the team lead by Yuri Oganessian and Vladimir Utyonkov in Dubna took aim with a stream of high energy calcium 48 ions. This rare, but naturally occurring isotope of calcium was blasted into the plutonium for 40 days, during which 5 million trillion ions were shot down the accelerator. Just one, single atom of the isotope 289 of element 114 was discovered, which took 30.4 seconds to decay.

The team at Dubna have since produced tiny quantities of isotopes 286, 287 and 288. Interestingly the half life of 30 seconds for that first atom has never been reproduced - all subsequent ununquadium 289 has had a half life of around 2.6 seconds, leading to speculation that the first experiment produced a special excited state of the nucleus called a nuclear isomer, a state which typical has an extra-long half life.

Unlike many transfermium elements, element 114 was predicted to fit well into its group in the periodic table. It is positioned in group 14, underneath lead. The first great success of the periodic table was Mendeleev's prediction of the existence of elements that had yet to be discovered. There were gaps in his table where he placed elements that he named after the element immediately above. He constructed the names by adding the prefix eka, which is Sanskrit for the number 'one'. So, Mendeleev said, we should have eka-boron, eka-aluminium, eka-manganese and eka-silicon.

Eka-silicon, for instance, is now called germanium and measured up well to Mendeleev's predictions. Similarly, for a long time it was assumed that element 114 would be eka-lead, with properties like that metal. Remarkably, however, although atoms have only been produced in ones and twos, there is some evidence that ununquadium behaves more like a noble gas than a metal.

This concept, still to be fully explored, is based on experiments where the element 114 atoms are passed down a tube with an inner coating of gold. Along the length of the tube, the temperature gradually decreases, dropping from 15 degrees Celsius to a chilly minus 185 degrees, gradually reducing the energy of the atoms passing along, making them easier to capture. The prediction is that a metal with lead-like properties should bind onto the gold easily, so will not get far down the tube. But a noble gas would have to be significantly chilled to undergo adsorption from the weak van der Waals force.

Rather than behaving like lead, element 114 seems to make it to the cold end of the tube before being captured, its position detected when it decays after a second or two. This experiment, conducted by Heinz Gäggeler of the Paul Scherrer Institute in Villigen, Switzerland, but working at Dubna is still only provisional, but the noble gas behaviour may be a result of relativistic effects.

Einstein's special relativity predicts that particles will get heavier and heavier as their velocity gets closer to the speed of light. A particle accelerated to around 42 per cent of the speed of light, for instance, will have a 10 per cent increase in mass. The expectation is that with an unusually high number of protons in the nucleus, the electrons will be moving fast enough to have relativistic effects that change the profile of their orbit, and hence the element's chemical properties.

With such few atoms to experiment with, the result is not yet certain. But something we do know for sure is that ununquadium is not just of interest to chemical train spotters.

Meera Senthilingam

That was science writer and chemical spotter Brian Clegg with the chemistry of element 114. Now next week, a dangerous yet useful element.

Andrea Sella

Because it's so volatile, you need to be really careful when you handle it since if you inhale it, it will decompose releasing poisonous carbon monoxide and dumping metallic nickel into your lungs. So it's very dangerous indeed. But in a way, that's the beauty of it: nickel carbonyl is incredibly fragile. If you heat it up it shakes itself to pieces, and you get both the nickel and the carbon monoxide back. So what Mond had was a deliciously simple way to separate and purify nickel from any other metal. And what is more, he could recycle the carbon monoxide.

Meera Senthilingam

And to find out the uses and chemistry of the pure form of nickel, as well as its compounds, join UCL's Andrea Sella in next week's Chemistry in its element. Until then I'm Meera Senthilingam and thank you for listening.


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