The atomic number of an atom is the number of protons found in its nucleus. The nucleus of an atom is the central core. Both protons and neutrons are found in the atomic nucleus.
The number of protons in the nucleus of an atom is the best way to determine the atomic number of an atom. Every carbon atom has 6 protons and an atomic number of 6. Oxygen has an atomic number of 8 and 8 protons in its nucleus.
In this image, helium has 2 protons, 2 electrons, and 2 neutrons. Because helium has 2 protons, it has an atomic number of 2.
