Which simplified electron configuration correctly represents aluminum (Al, atomic number 13)?

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

Answer: (D)