Question

what rule/principle states that electrons in the same sublevel (p, d, or f) are placed in individual orbitals, before they are paired up, to increase atomic stability?
aufbau principle
hunds rule
pauli exclusion principle

Explanation:

• The Aufbau principle is about filling orbitals from lower to higher energy levels.
• Hund's rule states that electrons in the same sublevel (p, d, f) occupy individual orbitals with parallel spins before pairing up to maximize stability.
• The Pauli exclusion principle states that no two electrons in an atom can have the same set of four quantum numbers.

So the rule described in the question is Hund's rule.

Answer:

B. Hund's rule