Atomic Number:

The number of protons in the nucleus plays is an important role in recognizes the atom in which it is given a special name, an atomic number. A symbol Z is frequent used for atomic number (or number of protons). The Hydrogen has an atomic number of 1 and lawrencium that has an atomic number of 103.  The atomic number is also equivalent to the number of electrons.

Atomic Mass Number

The sum of the whole number of protons, Z, and the whole number of neutrons, N, is known as the atomic mass number. The symbol is A. Not all atoms of the similar components have the similar atomic mass number, since, while the Z is the similar, the N and therefore the A are different.  Atoms of the similar component with different atomic mass numbers are known as isotopes.