Nuclear equations are used to describe radioactive decay, fission (spontaneous and induced) and fusion reactions.

Mass and energy equivalence must be maintained in nuclear equations.

All the particles (neutrons and protons) on one side should add up to be the same on the other side, in nuclear equations.

There will be a difference in the total mass of particles before and the total mass of particles after — this matter has been converted into energy.

There are different types of radioactive decay.

Fission reactions occur when a heavy nucleus splits into two nuclei of smaller mass number, plus some stray neutrons.

If there is no external input which causes the fission reaction, the nucleus naturally disintegrates, then it is spontaneous.

If the fission reaction is brought on by the initial bombardment of a neutron, then it is induced.

Fusion reactions occur when two lighter nuclei join together to form a heavier nucleus.

Nuclear fusion reactors require charged particles at a very high temperature (plasma) which have to be contained by magnetic fields. This is because high temperature plasma could melt the sides of the reactor or damage the container if it was not contained by magnetic fields. Containing it by magnetic fields ensures that the plasma cools down if it comes too close to the sides.

The following relationships is one of the most famous in physics, and it relates the mass of matter lost in nuclear reactions to the energy released.

$$ E=mc^2 $$