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    Why do 3 orbitals in the d sub shell have one energy and the other 2 another energy?

    We were looking at transition metals and there is an energy gap between 3 of the d orbitals and the remaining 2, effecting the colour appearing when light is absorbed. I don't understand why there is an energy gap though.

    Could someone explain? Sorry if stupid question
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    For an atom, with no ligands around it all 5 are the same energy.

    When you have ligands around the metal, they interact with the d orbitals and change their energy - the theory that I think you look at at A-level is called crystal field theory, though the much more accurate theory is ligand field theory.
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    It is the ligand sphere that causes a difference in energy. There is only a 3/2 spit in tetrahedral and octahedral complexes anyway, but it's caused by the manner in which the ligands interact with the d orbitals.
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    (Original post by itsConnor_)
    Why do 3 orbitals in the d sub shell have one energy and the other 2 another energy?

    We were looking at transition metals and there is an energy gap between 3 of the d orbitals and the remaining 2, effecting the colour appearing when light is absorbed. I don't understand why there is an energy gap though.

    Could someone explain? Sorry if stupid question
    The usual geometry for six ligands is octahedral.

    But the geometry of the d orbitals is different, with the sum of three of the orbitals presenting octahedral geometry (dxy, dxz, dyz) along three dimensional x, y, z axes and the other two (dx2-y2, dz2) "between" the three dimensional axes.

    To minimise interaction between the electrons of the incoming ligand and the 'd' orbitals the transition metal orientates so that the "octahedral" three orbitals lie as far apart from the ligand octahedral "cage" as possible.

    While this reduces the energy of the three octahedrally oriented orbitals it also puts the other two orbitals into more interacting positions, increasing their energy.

    The result is three 'd' orbitals with lower energy and two with higher energy.

    This 'd' orbital splitting only happens in this way in an octahedral ligand field. With other shaped complex ions the splitting pattern is different.
 
 
 
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