The maximum number of electrons that can be contained in an energy level (also called shells) is determined by the formula 2n^2, where n is the energy level; So, when n = 1, the maximum number of electrons is 2; when n = 2, the maximum number of electrons is 2*(2^2) = 8; when n = 3, the maximum number of electrons is 2 * (3^2) = 18; and when n=4, the maximum number of electrons is 2(4^2) = 32. So, briefly the series is 2, 8, 16, 32.
