Technetium caused me something of a headache. I struggled to think of a design, and found myself with a gap in the middle of my Periodic Table just as Mendeleev had over 150 years ago. For Mendeleev, the problem was never solved – technetium was not discovered until thirty years after his death – but thankfully I have been able to complete my transition elements with a reference to the way in which technetium was first synthesised.
The name technetium is taken from the Greek for ‘artificial’ because it was the first element to be artificially produced. Unlike all the elements around it in the periodic table, it is radioactive and this is why it was unknown in the time of Mendeleev – any mineral deposits of technetium once present in the Earth’s crust had long since decayed to other elements and simply weren’t there in sufficient quantity to be discovered.
In 1937 Italian scientists Emilio Segrè and Carlo Perrier were working at the University of Palermo in Sicily. Segrè had obtained some spare parts from the cyclotron in Berkeley – the machine Ernest Lawrence (see Lawrencium and Seaborgium) was using to smash atoms together. They analysed a piece of molybdenum foil from such an experiment and discovered not one but two isotopes of the missing element – the Berkeley team had created technetium without noticing and so Segrè and Perrier took the credit. My design shows the path taken by a particle in a cyclotron as it is accelerated by a large electromagnet and ultimately expelled at high speed.
Now we know how, we can make technetium in much greater quantities. It is in fact a significant by-product from nuclear power stations. The isotope Tc-99 has found significant use in medical imaging, enabling a wide variety of organs and glands to be visualised. It may be radioactive, but only a tiny amount is needed, it does not interfere with the body’s biochemistry and it is quickly excreted, all of which means the dose of radiation received is minimal and the benefits of diagnosis far outweigh any risk.
With thanks to Andy Brunning for prompting me to think about the cyclotron.