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6.11C: Structure - Fluorite (CaF₂)

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    2585
  • Calcium Fluoride is a solid and forms a cube like structure that is centralized around the calcium molecules. The crystal lattice structure that Calcium Fluoride is also known as the fluorite structure (Figure \(\PageIndex{1}\)) where the Ca2+ ions are eight-coordinate, being centered in a cube of eight F ions. Each F is coordinated to four Ca2+ in the shape of a tetrahedron.

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    Figure \(\PageIndex{1}\): Fluorite unit cell. (Public Domain; Benjah-bmm27 via Wikipedia)

    Calcium Fluoride is Quasilinear

    When Calcium Fluoride is in a single molecule it forms a Quasilinear structure. Quasilinear means the molecule resonates between a linear shape and a bent shape.Calcium Fluoride is a polyatomic molecule that contains one calcium molecule and two fluoride molecules. Calcium Fluoride is a quasilinear molecule the bonds are created from the single electrons of calcium and the single electron from fluoride. \(\ce{CaF2}\) has its electrons contained with in the 3d orbitals and are able to move between dyz and dz2 squared. The molecule in linear when they are in the dz2 orbitals the molecule is also the most stable in this shape. When the electrons are in the dyz orbitals the molecule becomes bent. The molecule resonates between these two shapes making it quasilinear. Figures two and three show how the d-orbitals cause the molecule to bend.

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    Fig # 1

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    Fig # 2 Fig # 3

    References

    1. Maushake, Peter. Calcium fluoride Chrystals. Wiley-VCH Verlag GmbH & CO. http://www.wiley-vch.de/berlin/journals/op/08-02/OP0802_S46-S47.pdf (October 07, 2010)
    2. Fergus, Jeffery W. The Application of Solid Fluoride Electrolytes in Chemical Sensors. Sensors and Actuators B: Chemical. Web Journal, 22. no 2. www.sciencedirect.com/science...f&searchtype=a (Oct 7, 2010)
    3. Housecroft, Catherine. Inorganic Chemistry. Pearson Prentice Hall 2008.