HKNIC - More recent ideas

More recent ideas
The classical view of the atom is far from the whole story. Further into the 20th century, the harder we have looked into the atom, the more subatomic particles we have discovered. Protons and neutrons are stable when they are in the nucleus, but they become somewhat unstable when they are set free. According to the current theory, these two subatomic particles are made up of more fundamental particles, known as leptons and hadrons.
Leptons are considered as truly fundamental particles, that is, they are not known to be made up of smaller particles. There are many categories of leptons, including electrons, positrons and neutrinos.
Hadrons are composite particles. They are strongly interacting, made up of something more fundamental and relatively massive. Protons and neutrons are examples of hadrons.
More recent ideas
A Hierarchy of Subatomic Particles

To study how we release and harness energy from the nucleus of an atom, however, it is usually enough for us to understand only the behaviour of protons, neutrons and electrons. Those who are really interested will need to look further into the physics of sub-atomic particles.