Further Ionisation Energies (Page 3 of 3) in pdf

Further Ionisation Energies Page 3

C h e m g u id e – a n s w e r s

c) K is [Ar] 4s

; Ca is [Ar] 4s

; Sc is [Ar] 3d

By the same logic as before, the second IE of potassium is coming from inner 3-level, whereas in

potassium and scandium it is still coming from the 4s level. Despite differences in the numbers of

protons, the second IE of potassium will be much higher than the other two because you are

removing an electron closer to the nucleus and much less screened.

d) This time, you are removing an inner electron (from the 3-level) in both potassium and calcium.

The 3d levels have much the same energies as the 4s level and so there is no major jump here – the

third scandium electron is still screened by all the 1- and 2-level electrons.

So you have a choice between potassium and calcium, with the electron being removed from a 2p

orbital in both cases, with the same screening. Now the extra proton in the calcium nucleus matters,

and calcium has the higher third IE.

Further Ionisation Energies Page 3