IMAT 2018 Q45 [First Ionisation Energy]

Five atoms are shown below. The letters are NOT chemical symbols.

Which one of the following atoms has the highest first ionisation energy?

A. _{11}^{23}Z

B. _{10}^{20}W

C. _{9}^{21}X

D. _{11}^{22}Y

E. _{9}^{19}V