A subatomic particle is any particle that is smaller than or makes up an atom. There are two types of sub-atomic particle: composite particles, which include protons, and fundamental particles, which include electrons. At one time this included protons, neutrons, and electrons, which are known to make up all elements (except ordinary hydrogen whoch does not contain any neutrons in its nucleus). Since that time, additional particles have been experimentally detected or theorized. These include quarks and gluons which are a level smaller still.
Other particles that exist are photons and neutrinos.
Most of space on the subatomic level is empty, with only very small amounts having particles in them.
Subatomic particles are categorized into:
- Fermions are "matter" particles, which include leptons (electrons and neutrinos) and hadrons (such as protons and neutrons).
- Bosons are "force carriers", which include photons (responsible for the electromagnetic interaction), gluons (responsible for the string nuclear force), the w and z bosons (responsible for the weak nuclear force) and the higgs boson (responsible for mass).
The graviton is a boson theorised by some models and would be responsible for gravitation. It has so far not been detected.