We all remember the Periodic Table of the Elements from our High School Science classes. You’ll remember that one of the things we were taught was that Uranium, element number 92, was the heaviest element that occurred naturally, all of the higher number elements had been manufactured in a labouratory using an ‘Atom Smasher’ or similar technology. The atomic number you’ll recall is simply the number of positively charged protons in the nucleus of any atom.
The first artificial element was manufactured in 1940 and was actually number 94 Plutonium, which was created by forcing alpha particles into a nucleus of Uranium. You may remember that alpha particles are actually the nucleus of Helium, element number 2, so adding element 2 to element 92 gets you element 94. In the years shortly after World War 2 many new elements were created by physicists. Starting in the 1960s however the pace began to slow as it became more and more difficult to produce heavier elements.
The reason for why making heavier elements became more difficult is actually the same as the reason why there are no naturally occurring elements beyond Uranium, radioactivity. In fact every element beyond Bismuth, element 83 is radioactive and will eventually decay into some lighter element. What’s actually going on is that the positively charged protons repel each other, in electricity it’s opposites charges that attract while similar charges repel after all. When you get more than about 80 protons in a nucleus even the nuclear glue, the so-called ‘Strong Force’ has trouble keeping the nucleus together.
Take Uranium with 92 protons for example, it has what’s called a half-life of about 4.5 billion years. What that means is, if you had 100 atoms of Uranium and waited 4.5 billion years half of those atoms would have decayed into some lighter element, only 50 would be left as Uranium. It’s a curious fact that since our Earth is also about 4.5 billion years old that means that today our planet only has half of the Uranium it originally had.
Many other elements have shorter half-lives than Uranium, Radium for example has a half life of only 1620 years making it very radioactive and therefore very dangerous. Plutonium, the first artificial element has a half life of about 80 million years, which still makes it kinda dangerous.
Anyway, the elements beyond Plutonium have very short half-lives, hours, minutes, even seconds and by the time you get to the heaviest element so far, Oganesson at number 118 it has a half life of only milliseconds. Indeed, Oganesson’s half life is so short that it was probably created a couple of years before its existence could be verified. The atoms just didn’t last long enough for the chemical checks to be completed that would make certain that it had been created.
The rules of Quantum Mechanics are strange and arcane however and the theoretical physicists who try to understand the nucleus have for several decades now been predicting that an ‘island of stability’ should exist from about element 120 to 126. Elements in this span are calculated to last for minutes if not hours or perhaps even longer, if only we could get there.
Now experimentalists at Lawrence Berkeley National Labouratory may have found the right technique. What they have succeeded in doing is to develop a beam of titanium nuclei, atoms of element 22 that have been completely stripped of their electrons. Using them to bombard atoms of Plutonium, element 94 the scientists have succeeded in producing the superheavy element Livermorium, number 116. The key factor here is that a pure beam of titanium nuclei something never before achieved with an element so high on the periodic table.
What the researchers at Lawrence Berkeley Labouratory plan to do now is to replace the Plutonium target with the element Californium, number 98 in order to produce element 120 and thereby reach the shore of that elusive island of stability. They expect that effort to take several years, Californium is both hard to get and hard to work with, but these scientists are the best in the world at handling superheavy elements.
Everything in our world, including our own bodies is made of such atoms and nuclei, by creating these new elements physicists learn more about both the particles making up the nucleus and the forces that keep it together, or force it apart.