Periodic table trends - electron affinity

[CaptainAmazon]

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I have had good luck with understanding the trends as opposed to memorizing them, but the only one that hasn't clicked is electron affinity. Why would having a greater electrostatic pull from the nucleus (Zeff) cause an element to dissipate more energy as it gains an electron (e- affinity increases)? I can't seem to picture this, so any help would be appreciated.

 

[PlsLetMeIn21]

Think about before and after. Before, the electron is just meandering around aimlessly. After, it's in a very happy and stable place if the nucleus has a strong attraction for it and a shell gets filled when it adds. The better the "after", the more energy it releases as it relaxes to a highly stable ("after") state.

The thing that messed with me was the sign convention.