1 s22 s21 \mathrm{~s}^{2} 2 \mathrm{~s}^{2}1 s22 s2
1s22s22p31 s^{2} 2 s^{2} 2 p^{3}1s22s22p3
1s22s22p21 s^{2} 2 s^{2} 2 p^{2}1s22s22p2
1s22s22p51 s^{2} 2 s^{2} 2 p^{5}1s22s22p5