Energy Equation: Electron Affinity

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Energy Equation: Electron Affinity

Postby Aashi_Patel_3B » Wed Oct 12, 2016 7:14 pm

Hi All,

I remember it was said in lecture that this is the first time change in energy is not final-initial.

The course reader mentions E= E(X)(g)-E(X-)(g). Is this neutral minus the ion? Overall, I'm just confused on why and how the final minus initial concept doesn't apply here.


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Re: Energy Equation: Electron Affinity

Postby Chem_Mod » Wed Oct 12, 2016 11:25 pm

Yes, I believe what E(x) - E(x-) that you have written is energy of the neutral atom - energy of the ion with 1 extra electron. So the current definition of electron affinity is the energy required to remove an electron from a negative ion. So by this definition, the equation above would make sense, E(x) being the final energy and E(x-) being the initial energy by the definition. However, historically, the definition was -E = E(x-) - E(x), which is the energy required to add an electron to the neutral atom. But, this definition was changed to avoid confusion and conversion of the sign change.

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