HW: 1.13

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Kelly Cai 4D
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Joined: Sat Jul 20, 2019 12:17 am

HW: 1.13

Postby Kelly Cai 4D » Fri Oct 25, 2019 8:46 pm

Ionization energies usually increase on going from left to right across the periodic table. The ionization energy for oxygen, however, is lower than that of either nitrogen or fluorine. Explain this anomaly.

Hannah Lee 2F
Posts: 117
Joined: Thu Jul 11, 2019 12:15 am

Re: HW: 1.13

Postby Hannah Lee 2F » Fri Oct 25, 2019 10:49 pm

Ionization energies usually increase on going from left to right across the periodic table. The ionization energy for oxygen, however, is lower than that of either nitrogen or fluorine. Explain this anomaly.


If you look at the filling of e- in the p-subshells for O, N, and F:
- N has three unpaired e- and half-filled orbital
- O has two unpaired e-, 1 paired e-
- F has one unpaired e-, 2 paired e-
Half-fulled or fully filled orbitals are more stable, and N has a half-filled p-orbital. Thus, oxygen is the first element in the p-block in which the p-electron must be paired. This adds electron-electron repulsion energy, causing ionization energy to be lower and making the electrons easier to remove because they're less stable. In the case of fluorine, because F is only one e- short of completing a full shell, it is more likely to gain rather than lose e- and thus would have a higher ionization energy than oxygen.

RRahimtoola1I
Posts: 102
Joined: Fri Aug 09, 2019 12:15 am

Re: HW: 1.13

Postby RRahimtoola1I » Sun Oct 27, 2019 11:21 am

Does anyone know if we could answer this question by saying that nitrogen has one electron in each orbital which has a higher stability and that fluorine has a high electron affinity because it wants an octet and doesn't want to lose an electron instead?

Do we have to mention electron repulsion?


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