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Homework Help: Chemistry, affinity

  1. Nov 26, 2008 #1
    In chemistry, what are the laws for finding electron affinity?
    i need to rate these elements, from highest electron affinity to lowest, using only a periodic table, and the laws of electron affinity
    Li K N C
    the answer is
    C> Li> K> N

    i then need to do the same for Ionization potential
  2. jcsd
  3. Nov 26, 2008 #2
    Electron affinity (EA) is essentially the energy released when an electron is added to a gas-phase atom. EA increases as you move from left to right across the periodic table. And it decreases as you move down the table. The same increase/decrease relationship can be applied to ionization energy (though I'm not 100% sure if ionization energy <=> ionization potential)
  4. Nov 27, 2008 #3
    from what i understand there are exception to that rule, something to do with symetry of the electron configuration,
    like in this excercise
    N is the furthest to the right and in the highest row of the 4 but has the smallest ea,
  5. Nov 27, 2008 #4

    we have just finished the Electron-negativity, Ionization Potential and Electron Affinity Chapter

    are you sure that N has the smallest EA???

    if i had given a question like the one above, my answer would be this:

    N > C > Li > K

    my answer is according to the Atomic Radius of each Atom

    as you can see N has the smallest Atomic Radius and K has the biggest.

    ( i'm sorry if my English is not understood :blushing:)
  6. Nov 27, 2008 #5
    http://www.rzuser.uni-heidelberg.de/~ltemgoua/chemistry/Electron_affinity.html [Broken]

    check it out, the numbers are the EA in Kj/mol, not exactly the way you guys say
    Last edited by a moderator: May 3, 2017
  7. Nov 27, 2008 #6
    hi again!

    I'm sorry, I think if this question was asked to students that specialized in Chemistry,
    They would have known about the exception.

    but for me I'm an 11th grade student.

    in answering either EA comparisons questions or any of the other related topics i follow the rule given in the link.

    "Eea increases across a period (row) (since the radius slightly decreases, because of the increased attraction from the nucleus, and the number of electrons in the top shell increases, helping the atom reach maximum stability) in the periodic table and decrease going down a group (family) (because of a large increase in radius and number of electrons that decrease the stability of the atom, repulsing each other)".

    but after seeing the link I think your answer is correct

    take care!
    Last edited by a moderator: May 3, 2017
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