What happens to to protons and neutrons during nuclear fusion?

Answer 1

It takes substantial energy - but it does happen, it's just difficult to achieve on earth.

However, the process of proton-proton fusion is one of the key reactions that takes place in the sun. 2 Hydrogen nuclei (protons) fuse to produce a deuterium nucleus (1 proton, 1 neutron) and a positron (positive electron). Subsequently, the deuterium nuclei can fuse with protons to form helium.

The electrostatic force provides substantial repulsion, hence the need for very high temperatures (about 15 million K). It is only at high temperatures that the KE of the protons is sufficient to overcome the electrostatic repulsion.

However, once you overcome electrostatics then the strong force will bind the 2 nucleons together - and produce a new nucleus. In the case of deuterium, and helium-3 and helium-4 the nuclei are stable. Tritium can also be produced, this is unstable and decays into helium-3.

There is a final catch - in that the temperatures of the sun aren't quite high enough to overcome the electrostatic repulsion between protons, so how can the reaction take place.

The solution is 'quantum tunneling' - A simple explanation: according to classical physics, if a particle doesn't has less energy than a barrier then the barrier acts like a brick wall - the particle can't cross it. In quantum mechanics, things are probability based - it's possible, for a particle to cross any barrier - the height of the barrier and the energy of the particle determine the probability that particle can cross. Occasionally, this means a particle can cross a barrier that is higher than its energy level - the particle appears to 'tunnel' through the barrier, instead of going over it. x TPS

Answer 2

If we are talking about fusion in the sun, it starts with protons (hydrogen nuclei), effectively two protons become neutrons, and the helium nucleus resulting is two protons plus two neutrons.

In the case of man made fusion on Earth, the probable reaction is deuterium (one proton plus one neutron) fusing with tritium (one proton plus two neutrons), the result is helium as above, together with a spare neutron which is ejected. These will be absorbed in the shielding material surrounding the fusion chamber.

Answer 3

During nuclear fusion, protons and neutrons come together to form a heavier nucleus. In this process, some of the mass of the protons and neutrons is converted into energy according to Einstein's famous equation E=mc^2. This release of energy powers the sun and other stars.

Answer 4

They react with each other, and depending on what elements they are coming from, that's how big or small the reaction is.