Electron Affinity  [ENDORSED]

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Aya Shokair- Dis 2H
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Joined: Fri Sep 29, 2017 7:07 am

Electron Affinity

Postby Aya Shokair- Dis 2H » Sun Nov 05, 2017 11:01 pm

Hi,
I know that Doctor Lavelle and the book says that electron affinity is not really periodic, but we still have to be able to compare elements and determine which would be higher/lower electron affinity energy. How are we supposed to do that?

Taylor 1F
Posts: 17
Joined: Thu Jul 27, 2017 3:00 am

Re: Electron Affinity

Postby Taylor 1F » Sun Nov 05, 2017 11:26 pm

You use the periodic table, but if there's a discrepancy you could use other factors like the electron configuration and it's atomic radius

CameronJohari1J
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Re: Electron Affinity

Postby CameronJohari1J » Sun Nov 05, 2017 11:36 pm

The general trend for electron affinity is that it increases across periods and decreases down groups with a few exceptions in the upper corner of the p-block. Group 15 elements generally have lower electron affinities than that of group 14 because the electron is entering an already half full p orbital and the effective nuclear charge experienced is less. Additionally, oxygen and sulfur both have a positive electron affinity for the first electron but have a negative value for the second electron.
Hope this helps.

Nora Sharp 1C
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Joined: Sat Jul 22, 2017 3:00 am

Re: Electron Affinity

Postby Nora Sharp 1C » Sun Nov 05, 2017 11:44 pm

There does seem to be many exceptions when following electron affinity down a period, but theres a trend that can be very loosely applied: electron affinity increases across a period and decreases down a group. There are explanations for some of the exceptions, though there are a lot of said exceptions: Cl has a higher electron affinity than F despite being lower down on the group because F is so electronegative it draws the electrons closer together, thus creating more electron-electron repulsion. Nitrogen is an exception because it has one electron each in the px, py, and pz orbitals, and therefore adding another electron into a p orbital that already has one electron in it requires some energy. Although, I can't understand why the book lists electron affinity for lithium as positive when it would make sense for it to be negative (isn't it strongly favored that lithium should lose electrons, not gain them?)

Michael Cheng 1C
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Re: Electron Affinity

Postby Michael Cheng 1C » Mon Nov 06, 2017 12:46 am

What is the difference between electron affinity and electronegativity?

Lauryn Jordan 1F
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Re: Electron Affinity

Postby Lauryn Jordan 1F » Mon Nov 06, 2017 8:29 am

Michael Cheng 1B wrote:What is the difference between electron affinity and electronegativity?



Electronegativity is how well an atom can attract electrons, while electron affinity is how much energy an atom releases when an electron is added.They both share the trend of increasing from bottom to top and left to right.

K Stefanescu 2I
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Joined: Fri Sep 29, 2017 7:04 am

Re: Electron Affinity  [ENDORSED]

Postby K Stefanescu 2I » Mon Nov 06, 2017 9:15 am

Regarding electronegativity and electron affinity, don't forget that if both of these values are high for an element, it will also have a high ionization energy. Ionization energy also follows both of these trends: increasing left to right and up each group.


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