Definition - What does Atomic Number mean?
The atomic number refers to the number of protons in an atom. It s symbolized by the letter z. The atomic number is found on the periodic table. In a neutral atom, the number of protons is equal to the number of electrons. The presence of positive charge on the nucleus is due to protons on the nucleus.
Safeopedia explains Atomic Number
The atomic number differs from the atomic mass of an atom. Protons and neutrons in the nucleus are collectively known as nucleons. The total number of nucleons in an atom is the mass number. So, the mass number is equal to the number of protons plus the number of neutrons in the atom. As an example, sulphur contains 16 protons and 16 neutrons, so it's atomic mass is 32, while it's atomic number is 16.