Step-by-step explanation:
The atomic number of an element is the number of protons an atom contains. This number helps differentiate one atom from the other. It is the basis by which elements are arranged on the periodic table.
The periodic table of elements follows the periodic law which shows that elements are arranged based on their atomic numbers.
Sodium Na;
Protons = 11
Electrons = 11
Neutrons = 12
Atomic number = 11