Nuclear fusion is when two smaller, lighter nuclei join to form a single larger and heavier nuclei. Stars use nuclear fusion reactions to produce energy
For example, two hydrogen nuclei can fuse together, under high temperature and pressure to form the nucleus of a helium isotope. A neutron will be released in the process and a large amount of energy.
Elements heavier than hydrogen are formed when lighter elements undergo nuclear fusion.
Nuclear fusion produces a lot of energy because some of the mass of the original nuclei is converted to energy, instead of being transferred to the new nucleus. This means that the mass of the final nucleus will be slightly less than the combined mass of the original nuclei.
Only a small amount is converted to energy in each reaction. However, when you combine the high number of reactions taking place, this produces a large amount of energy.
Another benefit to nuclear fusion is that it does not produce any radioactive waste. The process also requires hydrogen fuel, which can be made fairly easily.
An issue with nuclear fusion is that it only takes place at very high temperatures and pressures. This means that we cannot carry out nuclear fusion on Earth. However, there is a lot of research aiming to discover how we can use nuclear fusion at some point in the future.
The reason nuclear fusion requires such high temperatures is because the process involves the fusion of nuclei. As nuclei are positively charged, they will naturally repel each other. This means the nuclei must travel at a fast speed and fuse very quickly to overcome the electromagnetic repulsion.
Higher temperatures result in higher kinetic energy. So, to travel at such a high speed, the nuclei must travel in a hot gas or plasma that is at least 100,000,000 degrees Celsius (°C).
Try not to confuse nuclear fusion with nuclear fission.
Nuclear fusion is the joining of lighter nuclei to form heavier nuclei, which releases a large amount of energy in the process. Nuclear fusion takes place in the stars at very high temperatures and pressures.
Whereas, nuclear fission is when unstable nuclei split into smaller nuclei. This process releases a lot of energy but not as much as nuclear fusion. We use nuclear fission on Earth to generate electricity, This is because it can take place at much lower temperatures and pressures than nuclear fusion.