Question

Rank these elements according to first ionization energy..

I ranked them like this Ar Cl S P Si Al Mg Na but then it tells me that two elements should move up one spot in the ranking because of stable electrons configurations. Which ones would be moved up and why?

Answer 1

Your question should have stated if you want the IP increasing or decreasing. You have ranked them decreasing because Na must be the lowest and Ar must be the highest. I expect the two closed shell elements are Al and Mg. You can look up the first IP for each at www.webelements.com