I assume we examine the processes....
#F(g) + Delta_1rarrF^(+)(g) + e^-# #;Delta_1=1681*kJ*mol^-1#
#F^+(g) + Delta_2rarrF^(2+)(g) + e^-# #;Delta_2=3374.0*kJ*mol^-1#
#O(g) + Delta_1rarrO^(+)(g) + e^-# #;Delta_1=1313.9*kJ*mol^-1#
#O^+(g) + Delta_2rarrO^(2+)(g) + e^-# #;Delta_2=3388.3*kJ*mol^-1#
We use the data from this site.
#Delta_1# is entirely straightforward. Ionization energies should INCREASE across the Period, from left to right as we face the Table, and they does. However #Delta_2(O)# is marginally greater than #Delta_2(F)#. What's going on?
For fluorine's 2nd ionization we go from #1s^(2)2s^(2)2p^(4)# to #1s^(2)2s^(2)2p^(3)#; for oxygen we go from #1s^(2)2s^(2)2p^(3)# to #1s^(2)2s^(2)2p^(2)#. It is likely, therefore, that #O^+# gains some stability from Hund's rule of maximum multiplicity (as does nitrogen in its first ionization energy); this would tend to DECREASE #Delta_2#. On the other hand, #F^(2+)# is somewhat stabilized by the #"nitrogen atom-like"# electronic configuration, and this stability decreases the magnitude of #Delta_2#.
I would be interested in the rationalization your prof provides. Would you relate it here?
