Find the number of electron, protons and neutrons using atomic and mass number
Atomic number represent number of protons or electrons and Mass number represent total of protons + neutrons. For example, Consider N(nitrogen) with atomic number 7 and mass number 14. As atomic number represent number of proton or electron, hence, nitrogen contain 7 proton and 7 neutron and Mass number is 14 out of which 7 are proton, so remaining 7 are neutrons.
Number of sub-atomic particles in an element
Number of protons = number of electrons =Atomic number Number of neutrons = Atomic mass − atomic number