Elemental Disovery

If you have ever allowed you eyes to stray towards the nether regions of the periodic table of elements (it won’t mind) then you may have come across some elements with such exciting names as ununtrium, ununpentium, ununseptium and ununoctium. Now, everyone knows chemists are boring but these names really take the biscuit when it comes to  lack of imagination.

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Image credit: E. Otwell

What I hadn’t realised was that these humdrum elemental names were merely placeholders because the elements themselves had yet to be officially recognised. For over a decade teams of scientists around the world had been battling to come up with the data to prove that they really did exist.

Over the festive period you may have seen the official news of their discovery. The new elements; numbers 113, 115, 117 & 118; complete the 7th row of the periodic table. I’m going to tell you a little about the story of how the existence of element 113 was proven.

Scientists from the RIKEN lab in Japan first set out to discover 113 in 2003. Their technique was to take a piece of bismuth and bombard it with zinc ions travelling extremely fast, about 10% the speed of light. Within a year they had success. Two nuclei fused together to form a single atom of element 113. Very quickly, in less than one thousandth of a second, this highly unstable element emitted 3 alpha particles and decayed to dubnium262.  Within another year they saw a second event identical to the first one.

Now, I know what you’re thinking. They were at it for two years and they only created two atoms of the stuff? Well, yes. But that was actually seen as rapid progress. After this initial flurry of success there then followed seven years of nothingness. Seven years where not once did they manage to see the elusive new matter. Team leader Kosuke Morita did not lose heart, however:

“For over seven years we continued to search for data conclusively identifying element 113, but we just never saw another event. I was not prepared to give up, however, as I believed that one day, if we persevered, luck would fall upon us again.”

He was right. In 2012 a third event was seen and, crucially, this one was different to the first two. The first two underwent alpha decay to begin with but then underwent spontaneous fission once they had got the to dubnium262 phase. This meant that they could not precisely track the history of the atom and they couldn’t prove conclusively that what they saw was element 113. What they needed was to show that you could get from 113 down to a smaller atom with only alpha decays occurring.

The reason alpha particles are so desirable is that they are a known quantity, they are made up of two protons bound to two neutrons. If you have 1 atom of a known molecular weight and you detected x number of alpha particles in its creation then you can know for certain that the original atom was the mass of the end particle plus x times 4.

The third event at RIKEN was exactly what they needed. Element 113 went through six alpha decays thusly:

shot

Ununtrium became roentgenium and then so on through meitnerium, bohrium, dubnium, lawrencium and finally mendelevium. This was the home run that they had been looking for and why the Japanese team was awarded primacy over their main rival, a US/Russian collaboration, thereby marking the first time ever that an asian team has discovered an element.

As we all know, the best part about discovering something is that you get to name it. Sort of. They get to suggest names but ultimately it will be the International Union of Pure and Applied Chemistry that will pick, although it is extremely likely they will go with one of the suggestions. So far the RIKEN team in Japan have suggested japonium and rikenium, which rather leaves us where we started off ruing the lack of imagination amongst chemists.

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3 thoughts on “Elemental Disovery

  1. Nicely done…. Detailed enough to satisfy those who can find their way around the Table with some facility, yet simply presented, in such a way those without any background are able to follow… Every little bit helps keep the darkness at bay for as long as we have….

    gigoid, the dubious

    Like

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