The three major subatomic particles of an atom are electrons, neutrons and protons, according to Science Daily. Protons and neutrons are made of smaller particles known as quarks. Photons, positrons and neutrinos are made after nuclear fusion occurs in stars.
Protons and neutrons are found in the nucleus of an atom. Protons have a positive charge while neutrons have a neutral charge. Neutrons help hold protons together and maintain stable nuclei, according to the NDT Education Resource Center. Neutrons and protons are virtually identical.
Electrons are negatively charged particles that are outside the nucleus in the electron cloud. The University of California-Davis states electrons are the lightest of the three main particles in an atom, so much so that the mass of electrons is considered insignificant.
Atoms change properties when more subatomic particles are added to the nucleus. For example, a hydrogen atom has one proton, one neutron and one electron. A helium atom has two protons, two neutrons and two electrons. Unequal amounts of protons and electrons create charged atoms known as ions. Positively charged ions are cations and negatively charged ions are called anions.
Other subatomic particles exist, but only under extreme conditions such as the interior of stars and in particle accelerators. Positrons and neutrinos are given off when certain atoms become unstable.