Question: where do all the elements on the perodic table came from?

Andrea Cristini answered on 16 Jun 2014:

Around the beginning of time a couple billion years ago, the universe had cooled enough to form Hydrogen and a bit of Helium from protons and neutrons. Then when the first stars were formed they fused together elements which released energy, creating heavier elements. For stars around 10 times the mass of the sun (stars I am interested in) they start by ‘burning’ Hydrogen in their cores to create Helium, then Helium into Carbon, then Carbon into Neon, then Neon is blasted apart by high energy radiation into Oxygen and Helium, then Oxygen is ‘burnt’ into Silicon and finally Silicon into Iron.

Some other elements lighter than Iron (A=56) and some heavier (up to A~100) are produced in what is known as the s-process, where nuclei ‘capture’ slow moving neutrons and then convert some of these neutrons into protons (this is known as beta decay). Then intermediate mass elements (A~100 – A~150) are produced in the p process where nuclei ‘capture’ protons. Finally the heaviest of elements (A~150 – A~250) are created in the r-process which is the same as the s-process but with rapidly moving neutrons.

The s and p processes occur inside stars, we are not sure where the r process happens yet, but as very high energies are needed we think it might occur when stars explode as supernovae.