For a long time, alchemists tried to turn lead into gold. They sought the ‘philosopher’s stone’, a mysterious substance to create gold. But melting lead, adding chemicals and mixing it with other metals did not yield a precious metal to the alchemists. Professor of nuclear physics and goldsmith Piet Van Duppen of KU Leuven knows why: ‘They had no nuclear reactions.’
Making the core of gold
Before we can make gold, we have to zoom in quite a lot on the metal, down to the gold atom. Like a solar system, an atom consists of a nucleus and individual particles that orbit around it like planets. ‘The atomic nucleus is made up of a number of protons, which are the positive nuclear particles, and a number of neutrons, which are electrically neutral’, explains Van Duppen. How many protons a nucleus has determines what kind of element it is.
‘The lightest element, hydrogen, has one proton, the heaviest that we know now is oganesson with 118 protons. Gold is a bit in the middle, with 79 protons.’ There are exactly as many negatively charged electrons orbiting around the nucleus as the number of protons in the nucleus. That makes the atom electrically neutral. All those atoms stuck together form a gold nugget.
What alchemists did only affected the electron orbits. Van Duppen: ‘You can do that yourself in your backyard if you light a fire. It’s not that hard.’ It also requires relatively little energy, because even sunlight manipulates the electrons in the outermost orbits. ‘But if you want to make gold, you have to tackle the atomic nucleus. You need more energy for that. And you will find it in the stars.’
The gold on earth comes from stars
The gold on Earth today was created with the energy of nuclear reactions in stars that no longer exist. Van Duppen conducts research at CERN, the European center for nuclear research in France and Switzerland. ‘On Earth, we find nuclear reactions in the nuclear reactors or particle accelerators that we have at CERN.’ These devices give individual protons a gigantic speed, so that they can blast atomic nuclei to pieces like a bullet.
‘We filled a tube with lead and fired CERN’s protons at it.’ Occasionally a lead core breaks. ‘Lead has 82 protons. The impact of the fired proton on the atomic nucleus will shoot off maybe three protons. So from 82 we go to 79 protons and then we get gold. It’s that simple.’ Only three protons don’t go off with every shot. Sometimes there are more, sometimes less. For example, you can also make silver (47 protons) with a particle accelerator.
Making gold with a particle accelerator
The particle accelerator can make a million to a billion gold atoms per second. That sounds like a lot, but it does not mean that Van Duppen can fly to Saint-Tropez every week with a private jet. ‘I once calculated: it takes a hundred thousand years to make a ring of gold.’ And it not only takes time, it also eats up a lot of energy. The price tag of a particle accelerator is also slightly higher than that of a private jet.
Creating gold yourself is therefore not a gold mine. It is, however, a source of knowledge. ‘We are interested in the structure of atomic nuclei and in the prevailing forces between protons and neutrons. By making gold atoms, we learn something about those forces’, says Van Duppen.
Do you want to make gold yourself? It’s possible
Long story short: you can make gold if you have enough energy to manipulate the atomic nucleus. So that doesn’t work in your backyard as quickly. Unless you happen to have a particle accelerator or a nuclear reactor there.