Question

Which would have more electron affinity: O or O-?

Answer 1

What would you think on purely electrostatic grounds?

Explanation:

The electron affinity has been tabulated for atomic oxygen (of course, it is measured under specific conditions. Now, even though the 2nd reduction of oxygen anion (to give the dianion, `O^(2-)`) generates an electronically stable entity, I am willing to bet that it would be easier to reduce a NEUTRAL species, than an anion. Why? Well, on purely electrostatic grounds, it should be more difficult to add an electron to an already negative species.

How do we find an answer? I could not do so on the web, and I haven't got access to a good text. But please look at a text, and see if you can find successive electron affinities.