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### Electron Affinity

Posted: Sun Oct 27, 2019 12:38 pm
So the electron affinity of an element is the energy released when an electron is added to a gas phase atom. So my question is when doing calculations to determine the electron affinity of an element, what is the difference between a positive and negative electron affinity? What do they mean?

### Re: Electron Affinity

Posted: Sun Oct 27, 2019 12:39 pm
When its negative energy is released when an electron is added and when its positive energy is gained when an electron is added

### Re: Electron Affinity

Posted: Sun Oct 27, 2019 12:43 pm
When electron affinity is negative, it indicates that energy was released which means an electron was added. When electron affinity is positive, it indicates that energy was absorbed, which is required when actually producing an anion.

### Re: Electron Affinity

Posted: Sun Oct 27, 2019 4:18 pm
To add on to this, if it helps you to visualize it, the equation for electron affinity is the energy of the atom minus the energy of the anion. Therefore, having a positive electron affinity shows that energy is released when an e- is added to an atom. Then, when the electron affinity is negative, it means there isn't enough energy to add the e-, so energy must be supplied to force an e- onto an atom.

### Re: Electron Affinity

Posted: Sun Oct 27, 2019 8:48 pm
Okay, that makes more sense.

### Re: Electron Affinity

Posted: Sun Oct 27, 2019 9:19 pm
A negative electron affinity signifies a release of energy (exothermic reaction) and a positive electron affinity means more energy is needed than gained when adding the electron.

### Re: Electron Affinity

Posted: Sun Oct 27, 2019 11:32 pm
How can they measure the electron affinity? The way I think of it, I thought it was just described as how badly an atom wants to gain an electron. SO it takes less energy to add one as you move across the periodic table cause it gets closer to filling the octet. How can there be a negative energy?