Question

Which one of the following is a correct set for $Si{O}_2$ ?

• A. Trigonal planar
• B. Linear
• C. Tetrahedral
• D. Angular

Answer 1

The correct option is C Tetrahedral

$Si{O}_2$ is a covalent, 3-D network solid. Each Si atom is covalently bonded in a tetrahedral manner to four oxygen atoms.
Each oxygen atom in turn covalently bonded to another silicon atoms. Each corner is shared with another tetrahedron.
The entire crystal may be considered as giant molecule in which eight membered rings are formed with alternate silicon and oxygen atoms.

THEORY
Silicon Dioxide:

• Commonly known as silica, occurs in several crystallographic forms. Example: Quartz, Cristobalite, and Tridymite. They are interconvertible at a suitable temperature.
• $Si{O}_2$ is a covalent, 3-D network solid. Each Si atom is covalently bonded in a tetrahedral manner to four oxygen atoms.
• 
• Each oxygen atom in turn covalently bonded to another silicon atom. Each corner is shared with another tetrahedron.
• The entire crystal may be considered a giant molecule in which eight-membered rings are formed with alternate silicon and oxygen atoms.
• Si–O bond enthalpy is very high. That’s why silica in its normal form is almost non-reactive.
• It resists the attack by halogens, dihydrogen, and most of the acids and metals even at elevated temperatures. However, It is attacked by HF and NaOH. $Si{O}_2+4HF\to Si{F}_4+2H_{2}O$$Si{O}_2+2NaOH\to N{a}_{2}Si{O}_3+H_{2}O$