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Homework Help: Atomic and ionic radii

  1. Mar 29, 2014 #1
    1. I am a metal. My atomic radius is smaller than the atomic radius of the element with one fewer protons, but my +1 ionic radius is larger than the +1 ionic radius of the element with one fewer protons. Of the two elements in my group that have biological importance, I am the one with higher electro-negativity.

    NO relevant equations

    3. So, atomic radii size decreases across periods but increases down periods with the slight abnormalities in the 4th and 5th period once the d and f block orbitals are introduced. Originally I was thinking that this might apply to a group 1 metal, however all are larger than the noble gasses that have one less electron. Then I thought that Fe [Ar] 4s2 3d6 would be smaller than Mn [Ar]4s2 3d5 but fell down when Fe+ [Ar] 3d7 would still be smaller than Mn+ [Ar] 3d6. It would be greatly appreciated if someone could assist not only with the question itself but also with the differences relative ion radii sizes (which seems to be why I can not find an answer to this problem)

    Thanks in advance for any assistance
  2. jcsd
  3. Mar 29, 2014 #2


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    2017 Award

    Staff: Mentor

    That is a good approach, but this comparison (group 1 / noble gas) is needed for the +1 ionic radii where you have one electron less...
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