In 1913, Mosley introduced an atomic parameter called atomic number. Atomic number of an element is denoted by with, and can have only an integral value. According to him,
The atomic number is equal to the nuclear charge. The charge only the nucleus of an atom is equal to the number of protons inside its nucleus. So, the atomic number (Z) of an element is equal to the number of protons present inside the nucleus of its atom. That is,
Atomic number (Z) = No. of Protons (p) inside the nucleus
An atom has been no net charge on it. So, in an atom, the total number of electrons is equal to the number of protons inside its nucleus. Thus, in an atom, the total no. of electrons is equal to the atomic number of that element.