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Subshells and transition metals

  1. Apr 8, 2008 #1
    I have a question that my teacher can't answer. :(

    I get that with the electronic configurations for atoms, an s shell fills before a d shell but also empties before a d shell. Okay.

    So the last couple of subshells for iron are 4s2 3d6; Fe2+ would be 4s0 3d6 and Fe3+ would be 4s0 3d5.

    Am I right so far?

    My question is -- what happens if you add one electron to Fe3+? Which subshell does it go in? Do you get 4s0 3d6 (which violates the "s shell first" rule), or 4s1 3d5 (which gives you two different subshell configurations for Fe2+, depending on what it started as)?
  2. jcsd
  3. Apr 8, 2008 #2
    The most stable ion is where the subshell is half-filled. For Fe 2+, [Ar]3d5 4s1 would be more stable than [Ar]4s0 3d6.
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