How many unpaired electrons are in the p-orbitals of a fluorine atom?

Correct answer: 1

Explanation: Fluorine has atomic number 9 with electron configuration 1s² 2s² 2p⁵. The three 2p orbitals can hold 6 electrons; placing 5 electrons (Hund’s rule) gives two orbitals paired and one orbital with a single (unpaired) electron. Hence, there are 1 unpaired electron in the p-orbitals.

• 3 — Would be true for 2p³ (not 2p⁵).
• 0 — Would be true for 2p⁶ (all paired).
• 1 — Correct.
• 2 — Not possible for 2p⁵ under Hund’s rule.