Question

What principle or rule states that degenerate orbitals in the same subshell must be filled singly before being paired?

a) Hund's rule
b) Pauli's exclusion principle
c) Aufbau principle
d) Heisenberg's principle

Answer 1

The rule that requires degenerate orbitals within a subshell to be singly filled before electrons are paired is Hund's rule.

Step-by-step explanation:

The principle or rule that states that degenerate orbitals in the same subshell must be filled singly before being paired is known as Hund's rule. This rule specifically dictates that when you have multiple orbitals with the same energy within a subshell, each orbital must obtain one electron before any orbital gets a second electron. Additionally, these electrons must have the same spin direction. This contrasts with other principles, such as the Pauli exclusion principle, which requires that two electrons in the same orbital must have opposite spins, and the Aufbau principle, that outlines the order in which electrons fill up different orbital levels based on their energy.