Half-shell stability?

V2+

Fe3+

Fe2+

Ca2+

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  • 5 years ago
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    Half-shell stability ..... is a myth.....

    Some chemistry teachers are fond of saying that filled and half-filled sublevels are "somehow" more stable, as if by magic.

    The "stability" of a particular arrangement of electrons in an ion is a function of the energy of the ion. For instance, a situation where each orbital has one electron is lower in energy than there an orbital has two electrons (which repel each other). Such is the case for Fe2+ and Fe3+.

    The neutral iron atom.... 1s2, 2s2 2p6, 3s2 3p6 3d6, 4s2

    Fe2+ ion ....................... 1s2, 2s2 2p6, 3s2 3p6 3d6

    Fe3+ ion ....................... 1s2, 2s2 2p6, 3s2 3p6 3d5

    The Fe3+ ion has one electron in each of the 3d sublevels, and since there is no electron-electron repulsion in one of the orbitals as there is in Fe2+, the Fe3+ ion is at a lower energy.

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