An element 'A' is in group 2 of period 2 and another element 'B' is in the same group but in period 3. The proton number of 'A' is

In the modern periodic table, the first period has 2 elements, the second has 8 elements and the third also has 8 elements. The electronic configuration of ‘A’ is 2, 2 and the electronic configuration of ‘B’ is 2, 8, 2. In a neutral atom, number of protons is equal to the number of electrons. Hence, ‘A’ will have 8 protons less than 'B'.