Atoms of protons and neutrons in the nucleus and electrons outside the nucleus.
Different isotopes of elements will have different number of neutrons in the nucleus but the same number of protons.
Carbon 14
C-14
14C
Have a look at this image: https://upload.wikimedia.org/wikipedia/commons/1/18/Atomic_number_depiction.jpg
All are isotopes of carbon with total of 14 sub-atomic particles in the nucleus of the atom.
14 (total) - 6 (protons) = 8 neutrons