Concept question (2.81)

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Grace Boyd 2F
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Joined: Thu Jul 27, 2017 3:01 am

Concept question (2.81)

Postby Grace Boyd 2F » Tue Oct 24, 2017 1:21 am

Hi, this is more of a conceptual question but I am pretty confused by it and was wondering if anyone could please explain the answer to me.

"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."

Thank you!

Hannah Chew 2A
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Joined: Fri Sep 29, 2017 7:05 am
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Re: Concept question (2.81)

Postby Hannah Chew 2A » Tue Oct 24, 2017 10:02 am

So it makes sense that oxygen has a lower ionization energy than fluorine, as fluorine is more right on the periodic table and follows the above trend. However, the anomaly is that oxygen has a lower ionization energy than nitrogen. If we look at the electron configurations, oxygen is p4 while nitrogen is p3. Nitrogen has three unpaired electrons, while oxygen only has two. Oxygen is the first element to "pair" its electrons. This pairing of electron creates more electron-electron repulsions, and thus, the ionization energy of oxygen is lower than nitrogen, which doesn't have any paired electrons in the p orbital.

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