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    Why does sublevel 4s fill before 3d, even though 4s is in a higher energy level?
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    (Original post by Sani-Insanity)
    Why does sublevel 4s fill before 3d, even though 4s is in a higher energy level?
    As you get to higher orbitals, the order of energy levels get less distinct. The 4s and 3d orbitals are very close in energy, so that in some circumstances, it is more favourable to have electrons in the 3d orbital, and sometimes the 4s.
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    The 4s orbitals fill before the 3d orbitals, because the 4s orbitals have lower energy than the 3d orbitals...the orbitals with lower energy are always filled first, according to Aufbau's principle which states "all orbitals with the lowest energy must be filled first....".

    Hope this helps
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    (Original post by ScottishShortiex)
    The 4s orbitals fill before the 3d orbitals, because the 4s orbitals have lower energy than the 3d orbitals...the orbitals with lower energy are always filled first, according to Aufbau's principle which states "all orbitals with the lowest energy must be filled first....".

    Hope this helps
    My textbook says that the 4s orbital has a higher energy than the 3d though?
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    (Original post by Sani-Insanity)
    My textbook says that the 4s orbital has a higher energy than the 3d though?
    In my chemistry worksheets it just says that spectroscopic data shows that in the order of lowest energies is 4s then 3d! .
 
 
 
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