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Periodic trends and effective nuclear charge

  1. Jan 28, 2015 #1
    My book is trying to explain why atomic radii decreases as you move toward the right side of the periodic table because the effective nuclear charge increases. I understand why an increase in effective nuclear charge results in a smaller radius, but I don't know why the effective nuclear charge would decrease with more valence electrons. If Zeff= Z-S, then an increase in valence electrons would increase shielding; thus, Zeff would be smaller with an increase in S.
  2. jcsd
  3. Jan 28, 2015 #2


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    Staff: Mentor

    You increase the proton number Z by 1, but the new electron won't be completely inside so its shielding effect is less than one elementary charge.
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