Answer: Occupying singly first.
- A Pairing first
- B Occupying singly first
- C Skipping lower orbitals
- D Entering nucleus
Correct answer: B. Occupying singly first
Explanation: Hund's rule says electrons occupy degenerate orbitals singly with parallel spins before pairing.
Bohr's model: electrons occupy fixed circular shells (K, L, M) around the nucleus, with each shell holding up to 2n2 electrons.
Concept context
Explore how electrons are arranged inside an atom. Covers Bohr's model, quantum numbers, Heisenberg's uncertainty principle, shapes of s, p, d orbitals, and electronic configuration rules.