(10d) are Ionization Energy trends different from Electron Affinity trends?

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Jackie Ngo 1C
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Joined: Fri Sep 29, 2017 7:06 am

(10d) are Ionization Energy trends different from Electron Affinity trends?

Postby Jackie Ngo 1C » Sun Nov 04, 2018 4:49 pm

This is from problem 10d from the Garbreadium worksheet problems given at Lyndon's Saturday review session! It was said that the answer for "rank the following in order of increasing ionization energies" for the elements C, N, O, and F are C<O<N<F. However, Lyndon also brought up that for Electron Affinity, the ranks would change around to become N<C<O<F. Why is that so?

Mhun-Jeong Isaac Lee 1B
Posts: 54
Joined: Fri Sep 28, 2018 12:17 am

Re: (10d) are Ionization Energy trends different from Electron Affinity trends?

Postby Mhun-Jeong Isaac Lee 1B » Sun Nov 04, 2018 5:24 pm

So electron affinity is how much the element wants an electron. The reason why the order for increasing electron affinity is N<C<O<F instead of the intuitive C<N<O<F is because C wants to reach a half-filled subshell, or 3 electrons out of the 6 electrons in the p subshell. Half-filled and completely-filled are generally more stable. However, N already has a half-filled subshell so it is already relatively more stable. That's why C has a higher electron affinity than N.

Ionization energy is the energy it takes to remove an electron. The reason why the order for increasing ionization energy is C<O<N<F instead of the intuitive C<N<O<F is because taking an electron out of O would result in a half-filled 2p subshell which is more stable. While taking an electron from N would change it from a half-filled subshell to a subshell with 2 electrons. That's why N has a higher ionization energy than O.


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