What is the ground-state electron configuration of chlorine (Z = 17)?

• A. $1s^{2}2s^{2}2p^{6}3s^{2}3p^6$
• B. $1s^{2}2s^{2}2p^{5}3s^{2}3p^6$
• C. $1s^{2}2s^{2}2p^{6}3s^{1}3p^6$
• D. $1s^{2}2s^{2}2p^{6}3s^{2}3p^5$

Answer: (D)