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Arraging atoms/ions based on atomic radius

  1. Apr 5, 2004 #1
    Arranging atoms/ions based on atomic radius

    Hey, I'm in a bit of a bind here. I got a question that deals with atomic radius. The question asks to arrange the following atoms/ions in order from smallest to biggest:

    [tex]Cl, S^{2-}, K, K^{+}, O[/tex]

    I know just by looking at the periodic table that O has the smallest radius and that K has the largest radius... I also know that since [tex]S^{2-}[/tex] is larger than S and since S is larger than Cl that means [tex]S^{2-}[/tex] is also larger than Cl.

    [tex]K^{+}[/tex] is smaller than K and larger than Cl since it has a greater energy level.

    Here's my problem... I know that both [tex]K^{+}[/tex] and [tex]S^{2-}[/tex] fall somewhere between the Cl and K atoms.... and by looking up the actual radius of the [tex]K^{+}[/tex] and [tex]S^{2-}[/tex] ions I know that the [tex]S^{2-}[/tex] radius is larger than the [tex]K^{+}[/tex] radius but how do i prove this?

    Any help would be greatly appreaciated. Thanks!
    Last edited: Apr 5, 2004
  2. jcsd
  3. Apr 12, 2004 #2
    surely both K+ and S2- have the same number of electrons but different number of protons, since K+ has 3 more protons the overall attraction for electrons are stronger so smaller ionic radius?
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