1. The nucleus is in the ‘center’ of an atom
2. It is much smaller than the atom, and can often be treated as a point but sometimes cannot
3. It consists of positively charged protons and charge-less neutrons. These particles are composed of quarks.
4. Protons and neutrons are held together by a strong nuclear force which is attractive and much stronger than an electromagnetic force but quickly vanishes with the distance.
5. Protons and neutrons can turn into one another with the emission of electrons or positrons or by capturing electrons from the closest orbits. This is called beta decay. Weak nuclear interaction is involved here.
6. A nucleus can be unstable, and decay to more stable nuclei. During the decay, extra neutrons fly away with a large kinetic energy which can be used for electricity generation or for experiments involving neutron scattering.
7 A nucleus can be in different energetic states, similarly to an atom. When going from a high-energy state to a lower energy state, it emits gamma rays.