Final answer:
The correct statements regarding the placement of electrons in orbitals of the same sublevel are (B) Electrons with opposite spin must occupy the same orbital and (C) Electrons must fill orbitals of the same sublevel before pairing up, following Hund's rules and the Aufbau principle.
Step-by-step explanation:
In placing electrons in orbitals of the same sublevel, there are specific rules known as Hund's rules and the Aufbau principle that must be followed. The correct statements from the options provided are:
- (B) Electrons with opposite spin must occupy the same orbital.
- (C) Electrons must fill orbitals of the same sublevel before pairing up.
According to Hund's Rule, orbitals of equal energy (degenerate orbitals) are each occupied by one electron before any orbital is occupied by a second electron. More importantly, all singly occupied orbitals must have electrons with the same spin. Statement A is incorrect because electrons with the same spin do not need to occupy the same orbital, but instead should occupy separate orbitals until each orbital in the sublevel has one electron. Statement D is incorrect because electrons do not need to pair up before filling orbitals of the same sublevel; they should instead fill each orbital singly before pairing. The Aufbau principle guides us in filling the sublevels and orbitals in order of increasing energy to achieve the lowest possible energy configuration for an atom.