Final answer:
The element with 3 electrons in the 3p sublevel is phosphorus, following the electron filling order specified by the Aufbau principle and Hund's rule.
Step-by-step explanation:
The student's question pertains to the electronic structure of an element whose 3p sublevel contains 3 electrons. Based on the given information, we can infer that the element in question is one that follows the filling of the 3s subshell. With 3 electrons in the 3p sublevel, this means the element would be phosphorus, which has the electron configuration [Ne]3s23p3. The ordering of electron filling in atomic orbitals follows the Aufbau principle, starting with the lowest energy levels first (1s, 2s, 2p, 3s, then 3p).
In accordance with Hund's rule, these three electrons will occupy the three different 3p orbitals with parallel spins before any pairing occurs. This is because each p sublevel consists of three degenerate orbitals. The electronic configuration of phosphorus demonstrates this, with one electron in each of the three 3p orbitals.