What is the electron configuration for a ground-state atom with Z = 16?

What is the electron configuration for a ground-state atom with Z = 16?

• A. 1s2 2s2 2p6 3s2 3p4
• B. 1s2 2s2 2p6 3s2 3p3
• C. 1s2 2s2 2p5 3s2 3p4
• D. 1s2 2s2 2p6 3s1 3p5

Answer: (A)

This question tests how electrons occupy orbitals in the ground state according to the Aufbau principle: fill the lowest-energy subshells first, with up to two electrons per orbital, pairing spins as needed. For Z = 16, you have 16 electrons to place. Start with 1s2, then 2s2, then fill 2p6, bringing the count to 10. Next comes 3s2, bringing it to 12. The remaining four electrons go into the 3p subshell, giving 3p4. So the full ground-state configuration is 1s2 2s2 2p6 3s2 3p4. This matches sulfur’s electron configuration. The other patterns would either sum to a different total electron count or violate the order of filling (for example, 3p3 totals 15 electrons, and 3s1 3p5 would misorder how 3s and 3p are filled).

This question tests how electrons occupy orbitals in the ground state according to the Aufbau principle: fill the lowest-energy subshells first, with up to two electrons per orbital, pairing spins as needed. For Z = 16, you have 16 electrons to place. Start with 1s2, then 2s2, then fill 2p6, bringing the count to 10. Next comes 3s2, bringing it to 12. The remaining four electrons go into the 3p subshell, giving 3p4. So the full ground-state configuration is 1s2 2s2 2p6 3s2 3p4. This matches sulfur’s electron configuration. The other patterns would either sum to a different total electron count or violate the order of filling (for example, 3p3 totals 15 electrons, and 3s1 3p5 would misorder how 3s and 3p are filled).