Chemistry · Ch 11 — The p-Block Elements
Silicates
Silicates
Silicates
A large number of silicate minerals occur naturally, including feldspar, zeolites, mica and asbestos. The basic structural unit common to all silicates is the tetrahedral anion (Fig. 11.7: (a) the true tetrahedral geometry of one silicon bonded to four oxygens;
(b) a simplified schematic drawing of the same unit).
In different silicate minerals, this tetrahedral unit either occurs as an isolated, discrete ion, or many such tetrahedra link together by sharing 1, 2, 3 or 4 of their oxygen corners with neighbouring tetrahedra. Depending on how many corners are shared, the linked units build up chain, ring, sheet, or fully three-dimensional network structures — sharing all four corners of every tetrahedron gives a complete 3-D network. The residual negative charge left on the silicate framework is balanced by positively charged metal cations.
Two important man-made silicates in everyday use are glass and cement. …
What this figure shows. Two small side-by-side sketches labelled (a) and (b). Sketch (a) shows a silicon atom (labelled 'Si') at the centre with four oxygen atoms (each labelled 'O' with a negative charge) positioned around it — three connected by solid lines and one by a dashed line — arranged so the overall shape reads as a tetrahedron with the dashed bond indicating the atom pointing away from the viewer. Sketch (b) is a simplified schematic version of the same unit: a small central dot (representing silicon) surrounded by four open circles (representing oxygen atoms) connected by solid and dashed lines in a triangular tetrahedral outline, with a legend below reading 'Silicon' (dot symbol) and 'O …