Final answer:
The correct electron configuration is D) 1s²2s²2p¶3s²3p³, which indicates the third energy level has 5 electrons, with 3s fully occupied and 3 electrons in the 3p orbital.
Step-by-step explanation:
The correct answer for an element with 5 electrons in the third energy level is D) 1s²2s²2p¶3s²3p³. The electron configuration should follow the Aufbau principle, which states that electrons fill orbitals starting at the lowest available energy level before moving to higher levels. Since the third energy level can contain up to 18 electrons (2 in the 3s, 6 in the 3p, and 10 in the 3d orbitals), having 5 electrons means that the 3s orbital is fully occupied with 2 electrons, and the 3p orbital has 3 electrons.