Atomic nuclei have two kinds of subatomic particles, which are protons and neutrons.
The proton and the neutron. Both of them, in turn, are made up of quarks.
The atomic number of an atom is the number of protons in the atom. The identity of an atom is based on its atomic number, so a change in the number of protons mean an atom has turned into a different...
Number of protons in the nucleus is the atomic number.
Protons.