Number of protons = number of electrons outside the nucleus = atomic number. According to relevant mathematical data, we know that the charge number of the central atom = the number of electrons outside the nucleus = the atomic number. In atoms, the number of positive charges carried by the nucleus = the number of protons = the number of electrons outside the nucleus = the atomic number. In atoms, the number of positive charges carried by the nucleus is equal to the number of protons, the number of electrons outside the nucleus and the atomic number.