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Explain silicon dioxide. |
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Answer» Solution :95% of the earth.s crust is MADE up of silica and silicates. Silicon dioxide, commonly known as silica, occurs in several crystallographic forms. Silica is found in the form of quartz, CRISTOBALITE and tridymite. Silicon dioxide is a covalent, three-dimensional network solid in which each silicon atom is covalently bonded in a tetrahedral manner to four oxygen atoms. Each oxygen atom in turn covalently bonded to another silicon atoms. The entire crystal may be considered as giant molecule in which eight membered rings are formed with alternate silicon and oxygen atoms.  Silica in its normal form is ALMOST non-reactive because of very high Si - O bond enthalpy. It resists the attack by halogens, dihydrogen and most of the acids and metals even at elevated temperatures. `SiO_2` REACTS with HF and NaOH. `SiO_2 + 2NaOH to Na_2SiO_2 + H_2O` `SiO_2 + 4HF to SiF_4 + 2H_2O` |
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