Atomic number, mass number and isotopes

Nuclides, atomic number and mass number A nuclide is a particular type of atom and possesses a characteristic atomic number, Z, which is equal to the number of protons in the nucleus; because the atom is electrically neutral, Z also equals the number of electrons. The mass number, A, of a nuclide is the number of protons and neutrons in the nucleus. A shorthand method of showing the atomic number and mass number of a nuclide along with its symbol, E, is:

Atomic number = Z= number of protons in the nucleus = number of electrons

Mass number =A= number of protons ‏ number of neutrons

Number of neutrons=A- Z