There are two energy sublevels in the second principal energy level. These two energy sublevels are 2s and 2p. The energy distribution in an atom is divided into a number of principal energy levels, and the principal energy levels are again divided into four basic energy sublevels.
The sublevels are s (sharp), p (principle), d (diffuse) and f (fundamental). The s sublevel can hold two electrons, and the p sublevel can hold six electrons. Therefore, the second principal energy level can hold a total of eight electrons in the 2s and 2p sublevels. Eight is the maximum number of electrons that the second principal energy level needs to fill its octet.