The subatomic particles of protons and neutrons are found in the nucleus of an atom. Protons are particles with a positive charge, while neutrons have no charge. Electrons, which have a negative charge, are particles that can found orbiting outside the nucleus of an atom.
Every atom has a specific set of identical protons and identical neutrons. Neutrons hold the protons together in the nucleus, since the positive charge of the protons would repel each other. The number of protons and neutrons in the nucleus gives each atom its own characteristics and helps differentiate it from another atom. For example, a helium atom has two protons and two neutrons, while a hydrogen atom has one proton and one neutron and a beryllium atom has four protons and four neutrons.