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Why is electron gain enthalpy generally exothermic?

  1. Jul 14, 2015 #1
    I understand that we need to supply energy to counter the nuclear attraction when we remove electrons and that is the reason ionization energy is endothermic. However, why does an atom release energy when we add an electron to it? And also why do some elements( like the halogens) release more energy than the rest? I can understand that it is easier for them to gain electrons than the others because of small size and increase in nuclear charge and I guess it just goes to the first question again.
    Please help.
  2. jcsd
  3. Jul 14, 2015 #2

    Andrew Mason

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    When an atom gains an electron there must be a net force of attraction between the atom and electron. So for the atom to gain an electron, would that require energy being added from the surroundings?

  4. Jul 14, 2015 #3
    I really can't figure it out. How does the force of attraction relate to whether it releases energy or not?
  5. Jul 15, 2015 #4
    That electron has some energy associated with it. So when the electron becomes bound to the nucleus, where does all that (or some of that) energy go?
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