Structure of pure silica
In silica, each atom of silicon is bonded with four oxygen atoms and each atom of oxygen is bonded with two silicon atoms. The elemental tetrahedral of silica are joined at the vertices to give the hexagonal network in three dimensions. The structure of pure solid and molten silica is shown in the figure
| Figure 4.1: |
Structure of silica (a) solid and (b) molten |
As seen in the figure 4.1a, each tetrahedron is joined at the vertex so as to obtain the three dimensional hexagonal network. During melting the crystalline network of silica is broken by thermal agitation as shown on figure 4.1b. Only at very high temperatures, molten silica consists of equal number of  and  ions.
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