Question

states that every orbital in a subshell must be occupied by one electron before any orbital in that same subshell can be occupied by a second electron.

Explanation:

This is a concept related to electron configuration in atoms. Hund's rule specifically addresses the filling of orbitals in a subshell. It emphasizes that electrons first occupy each orbital in a subshell singly with parallel spins before pairing up.

Answer:

Hund's rule