# 6.11C: Structure - Fluorite ($$CaF2$$)

This page is going to discuss the structure of the molecule calcium fluoride. This molecule is polyatomic the contains sixteen valance electrons that help to form the bounds of this molecule. These bounds and remaining lone pairs of electrons are going to determine the structure and shape of the molecule.

### Introduction

Calcium Fluoride is a solid and when their are multiple molecules around they form 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# 1 shows what Calcium Fluoride looks like when its in the crystal lattice structure. 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.

### Why CaF2 is Quasilinear

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. 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.

Fig # 1

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. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THH-3S9D1DP-3R&_user=10&_coverDate=07%2F31%2F1997&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1489306299&_rerunOrigin=scholar.google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=1690b74413f7ed3066d62c941e7eb79f&searchtype=a (Oct 7, 2010)
3. Housecroft, Catherine. Inorganic Chemistry. Pearson Prentice Hall 2008.

### Problems

1. Q. How is CaF2 made in in the lab?

A.  It is made by mixing Calcium Carbonate and hydrofluoric acid to give calcium fluoride, carbon dioxide, and water.

2. Q. Is CaF2 a polar molecule?

A. In the Linear shape CaF2 is non-polar, but in the bent shape it becomes polar.

3. Q. Is CaF2 a covalent or ionic molecule?

A. The molecule is covalent because each of the atoms are sharing an elelectrons to form the bonds.

4. Q. How Many total electron are there in the CaF2 Molecule?

A. There are 16 electrons in CaF2.

5. Q. Why is CaF2 Molecule bent when the electrons are in the dyz orbitals?

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