Electron configuration in the second shell of oxygen

Steps:

• Atom with 8 protons is neutral oxygen (8 electrons).
• Full configuration: 1s² 2s² 2p⁴ (follows Aufbau principle).
• Second shell (n=2) includes 2s (max 2 electrons) and 2p (max 6 electrons) subshells.
• Distribution: 2s² (s 2) and 2p⁴ (p 4), totaling 6 electrons.

Why D is correct:

• s 2 p 4 follows the order of filling (s before p) and Pauli exclusion principle, with s holding exactly 2 electrons.

Why the others are wrong:

• A: Incorrect order (p before s) and s exceeds maximum 2 electrons.
• B: s subshell cannot hold 4 electrons (maximum 2 per orbital, 2 orbitals).
• C: Incorrect order (p before s) and violates subshell capacities.

Final answer: D