Ionization Potential

[yxgao]

Which of the following atoms has the lowest ionization potential?
a. 2 4 He
b. 7 14 N
c. 8 16 O
d. 18 40 Ar
e. 55 133 Cs

The answer is e. Can someone explain the general concepts and reasoning behind this? Thanks,
--YG

[csmines]

In my humble opinion this is dirty chemistry....[g)] The theory behind this goes back to electron shells in elementary chemistry for example the s1, s2, p1, s3, p2, d1 and so on. It is a matter of knowing which shells fill how man 'slots' there are in each level and intuiting the qualitative ionization potential. The s shells have 2 slots, the p shells have 6, the d shells have 10,and the f shells have 14... You can figure out where the electrons are with simple subtraction knowing the patterns of filling. Remember that the s orbitals of the n+1 level typically fill before the d orbitals of level n. It's easy to note the pattern of Ionization potential when shown a chart of them, check one out it'll be a tremendous help.

A) He; Helium is going to have a relatively high ionization potential because it has only two electrons which completely fill the lowest (and closest to positive nucleus) energy shell. {2 electrons in S1} 24.5 eV

B) N; Nitrogen fills up the lowest energy shell the s2 orbital and half of the p1 orbital (half an orbital is stabilier than half +1 of an orbital in the lower atomic numbers).{2 in S1, 2 in S2, and 3 in p1} 14.5eV

C) O; Oxygen is Nitrogen plus one and as mentioned above half a full orbital is stabiler than half plus one at this atomic level.{2 in S1, 2 in S2, 4 in p1} 13.6eV

D) Ar; Argon has filled S1, S2, P1, S3, and P1. Since it has filled them it has a high ionization potential of 15.8 eV.

E) Cs; Cesium is by far the best choice of these elements for the lowest ionization energy. It has S1->5 filled, p1->3 filled, and d1 and 2 filled. There is a lonesome electron in the 6th S orbital that is far out from the nucleus which is very easily removed due to it's distance and the fact that it is alone in an orbital. {2 in S1->5, 6 in p1->3, 10 in d1,2 and only 1 in S6.} IP of 3.9eV

I hope this helped, I'm not the best at exlpaining stupid chemistry!

Bored CSMPhysicist