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Understanding electron affinity

  1. Oct 9, 2011 #1
    Hello everyone, I am learning some chemistry and have come across a topic that I cannot get my mind around.

    I understand that electron affinity is the energy given off/absorbed when an electron is taken in by atom. Atoms with low ionization energies tend to have low negative/positive electron affinities. What confuses me is the book also states that the first electron affinity is generally negative with the second one being positive (isn't EA positive when releasing electrons?) due to the atom needing to absorb more energy to overcome the electrostatic repulsions of the first electron. What i was thinking is why do atoms/ions (nonmetals) with a higher number of valence electrons have higher NEGATIVE electron affinities and not low negative/positive electron affinities if there's more electrons to overcome in the outer shell? Wouldn't the ion need more energy to deal with the new electrons moreso than the metals? I just seem to be contradicting myself here, help me get my thinking back on track.

    Edit: Alright I believe I may have figured it out...The nonmetals (except group 8A) readily accept electrons, giving them the high negative charge while metals once they gain an electron the second one isn't as readily accepted due to outer electron configuration and needs to absorb energy to overcome the electrostatic repulsion.

    Thanks for the reply!
     
    Last edited: Oct 9, 2011
  2. jcsd
  3. Oct 9, 2011 #2

    Drakkith

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    Staff: Mentor

    I THINK it is because an atom is more stable when it fills its outer electron shell. Atoms near the last column only need 1-2 more electrons to fill it and so attract electrons better than atoms near the 1st column, which need to get rid of electrons to reach it. Do you know much about electron orbitals and shells?
     
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