History
In the 1600s, Johannes Kepler speculated on the symmetry of snowflakes and also on the close packing of spherical objects such as fruit (this problem remained unsolved until very recently). The symmetrical arrangement of closely packed spheres informed theories of molecular structure in the late 1800s, and many theories of crystallography and solid state inorganic structure used collections of equal and unequal spheres to simulate packing and predict structure.
John Dalton represented compounds as aggregations of circular atoms, and although Loschmidt did not create physical models, his diagrams based on circles are two-dimensional analogues of later models. Hofmann is credited with the first physical molecular model around 1860 (Fig. 1). Note how the size of the carbon appears smaller than the hydrogen. The importance of stereochemistry was not then recognised and the model is essentially topological (it should be a 3-dimensional tetrahedron).
J.H. van 't Hoff and J. le Bel introduced the concept of chemistry in space—stereochemistry in three dimensions. van 't Hoff built tetrahedral molecules representing the three-dimensional properties of carbon.
Read more about this topic: Molecular Model
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