Definition - What does Atomic Number mean?
Atomic Number is the number of protons present in the nucleus of an element. It is similar to the charge number of the nucleus and is represented by symbol Z. It is used to uniquely identify a chemical element. Atomic Number is equal to the number of electrons in an uncharged atom. It is confused with the mass number which represented by symbol A, which is referred to as the total number of neutrons and protons in a nucleus. The neutron number, N, is the number of neutrons present in the nucleus. Hence mass number, A, is equal to the sum of the Atomic Number and neutron number.
Petropedia explains Atomic Number
Atoms which have the same Atomic Number, different neutron number and different atomic masses and are called isotopes. All elements have specific chemical properties, which are the consequences of the number of electrons in the neutral atom, known as Atomic Number. An element has a unique number which identifies the number of protons present in the atom of that element. This number is constant, which means that the number of protons present in the nucleus never changes. Protons play an important role in the atomic structure of an element and thus the number of protons in a nucleus can be referred as the Atomic Number of that element.