How are elements such as gold created and why can’t humans creat
In: Chemistry
To expand on the rest of the elements:
Hydrogen exists without anything else because it’s the simplest, most stable form that you get with the rules of the universe – one proton, one electron probably, and maybe a neutron or two.
During the birth of the universe when everything was super hot and dense, some hydrogen was fused by that heat into helium, and perhaps a very small amount of those two were fused into lithium.
Everything between hydrogen and iron comes from stars fusing elements during their normal lifespan. Fusing heavier elements requires more force and provides less energy, so it requires larger stars with more gravity crushing into the core. Main sequence stars like our Sun only fuse hydrogen into helium, and then as a red giant they will fuse some hydrogen and helium into heavier elements, up to maybe carbon and oxygen. Once it runs out of hydrogen and helium, it’ll shrink down into a white dwarf and then cool to a black dwarf.
Fusing elements into iron or anything heavier doesn’t give any energy back at all. You can get more energy out with fission, instead. Stars with enough mass will keep fusing heavier and heavier elements until they start fusing iron. Once this happens, the star will collapse very quickly. Stars are held up against their own gravity by the energy produced through fusion. When they start fusing iron, it sucks up energy which means there’s nothing holding the star up against itself. The outer layers of the star can reach high fractions of the speed of light before slamming into the super dense core. That energy creates another wave of fusion that creates all the elements heavier than iron. It also creates an explosion – a nova or supernova – which blasts the star apart into a nebula and spreads all those elements out into the universe.
It’s likely that different heavy elements are more common in different kinds of novae. For example, many stars are part of binary or trinary systems with stars close together. The larger of the two stars can siphon material away from its partner, getting larger until it explodes. This “type 1a supernova” might be responsible for more of certain elements, while a type 2 supernova (a large star collapsing on its own) might produce more of other elements. Astrophysicists are still figuring that out. Regardless, heavy elements come from supernovae.
Many elements are abundant because they are the decay products of larger, radioactive elements. So, the supernova creates uranium, and the uranium decays into thorium and radium and so on.
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