Final answer:
The second Principal Energy Level (PEL) contains the 2s and 2p sublevels, with 2s being filled before 2p according to the Aufbau principle. The 2p sublevel has three orbitals, each occupied by one electron before any is doubly occupied as per Hund's rule, accommodating six electrons in total.
Step-by-step explanation:
The second Principal Energy Level (PEL) includes two sublevels: the 2s and the 2p sublevels. The 2s sublevel is filled first according to the Aufbau principle, which states that orbitals are filled with electrons in order of increasing energy. The 2s sublevel consists of one orbital, which can hold two electrons, as seen in lithium (Li) and beryllium (Be). After the 2s sublevel is filled, electrons begin to occupy the 2p sublevel, which consists of three orbitals, allowing for a total of six electrons.
Each 2p orbital can hold two electrons, but according to Hund's rule, each orbital is singly occupied before any orbital is doubly occupied. Therefore, when adding the sixth electron in the 2p sublevel, it will enter the second p orbital with the same spin as the fifth electron. In summary, the 2nd PEL consists of 2s and 2p sublevels, with the 2s sublevel being filled first with two electrons followed by the three 2p orbitals, which can accommodate a total of six electrons, completing the sublevel with elements B through Ne.