What is the difference between the atoms of different chemical elements?

Each chemical element is located under its own serial number in the periodic table of Mendeleev. This number corresponds to the number of protons and the number of electrons in the atom, as well as the quantitative measure of the nuclear charge of the given atom. In addition, each element has its own atomic mass shown in the table. The number of neutrons in the nucleus of an atom is determined by the difference between the atomic mass and the ordinal number of the element.