Which electron configuration represents the ground-state neutral sulfur atom?

Which electron configuration represents the ground-state neutral sulfur atom?

• A. 1s2 2s2 2p6 3s2 3p4
• B. 1s2 2s2 2p6 3s2 3p5
• C. 1s2 2s2 2p4 3s2 3p6
• D. 1s2 2s2 2p5 3s2 3p4

Answer: (A)

Filling electrons goes from the lowest energy levels upward. Sulfur has 16 electrons, so after the inner shells that match a neon-like core (1s2 2s2 2p6), the remaining six electrons occupy the third shell: 3s2 then 3p4. This gives the ground-state neutral configuration 1s2 2s2 2p6 3s2 3p4, which also reflects sulfur’s six valence electrons (group 16). Choosing the other options would misplace electrons in the third shell or in the second shell: a 3p5 arrangement would suggest seven valence electrons, not six; a 2p4 arrangement would indicate an incomplete core with an unusual inner-shell structure; a 2p5 arrangement would contradict the allowable distribution for a total of 16 electrons.

Filling electrons goes from the lowest energy levels upward. Sulfur has 16 electrons, so after the inner shells that match a neon-like core (1s2 2s2 2p6), the remaining six electrons occupy the third shell: 3s2 then 3p4. This gives the ground-state neutral configuration 1s2 2s2 2p6 3s2 3p4, which also reflects sulfur’s six valence electrons (group 16).

Choosing the other options would misplace electrons in the third shell or in the second shell: a 3p5 arrangement would suggest seven valence electrons, not six; a 2p4 arrangement would indicate an incomplete core with an unusual inner-shell structure; a 2p5 arrangement would contradict the allowable distribution for a total of 16 electrons.