How many occupied electron shells does a neutral oxygen atom have in its ground-state electron configuration?

• A. 8 shells
• B. 3 shells
• C. 2 shells
• D. 1 shell

Answer: (C)

Verified step by step guidance

1. Recall that the number of occupied electron shells corresponds to the number of principal energy levels that contain electrons in the atom's ground state.
2. Determine the atomic number of oxygen, which is 8, meaning it has 8 electrons in a neutral atom.
3. Write the ground-state electron configuration of oxygen by filling electrons into shells and subshells following the Aufbau principle: \$1s^2 2s^2 2p^4$.
4. Identify the principal quantum numbers (shell numbers) present in the configuration: electrons occupy the first shell (n=1) and the second shell (n=2).
5. Conclude that since electrons are present only in shells 1 and 2, oxygen has 2 occupied electron shells in its ground state.