[ygao85]

For the ionization energy, the trend is that it increases as we move from left to right across a period. However, when we go from N to O, the IP is lower b/c all 3 orbitals are being occupied and the electron of O hs to be put in a orbital which already contains a electron. Therefore electron-electron repulsion occurs and O has a ower IP than N. This is true for P and As.

But when we get to Sb and Bi, the IP of the next elements INCREASES and doesn't follow the above rule. How come?
Thank you.

[madscientist]

Periodic trends are general rules that dont necessarily apply to all elements.

there exceptions to the rule.

for example the boiling points generally increase with atomic/molecular mass, but not always.

hope this was your queery. ( im pretty new to chemistry)

cheers,

madscientist