Chapter 6, Problem 6.63SP

Three atoms have the following electron configurations:
(a) $1s^{2}2s^{2}2p^{6}3s^{2}3p^1$
(b) $1s^{2}2s^{2}2p^{6}3s^{2}3p^5$
(c) $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^1$
Which of the three has the largest $E_{i1}$ ? Which has thesmallest $E_{i4}$ ?