From The School of Biomedical Sciences Wiki
The atomic number is the number of protons that are found in the nucleus of an atom. It may also be refered to as the proton'number.' An atom that has a neutral charge, will have equal numbers of protons and electrons, therefore meaning the atomic number is equivalent to the the number of electrons.
In chemistry and physics the atomic number is represented using the symbol Z.
When looking at a periodic table, the atomic number will be found at the top of the box for each element.