Describe the structure of and bonding in silicon and silicon dioxide


Silicon:
Silicon is the eighth most common element on earth by mass and has the symbol Si with an atomic number of 14. It has the electronic configuration of [Ne] 3s2 3p2
558px-Electron_shell_014_Silicon.svg.pngsio2.gif
Silicon has a giant covalent structure, held together by strong molecular bonds.
It is commonly found in it's solid state and is used as a semi-conductor in micro controllers, resistors, diodes...
As it is a semi conductor, it readily shares and gives away it's four valence electrons, hence having many different forms of chemical bonding. This property hence also allows it to be made into Glass, Abrasives, Pottery and even Silly Putty.
It is an amphoteric oxide with an oxidation state of 1,2,3,4 (-1,-2,-3,-4). Silicon crystalizes in to a diamond cubic crystal structure as shown below:
628px-Silicon-unit-cell-3D-balls.png
Silicon Dioxide:
Silicon dioxide has a chemical formula of SiO2 and is most commonly known as silica. Silica is most commonly found in nature as sand or quartz and is mainly used to produce glass.
Silicates often are found with a tetrahedral coordination, with 4 oxygens surrounding a silicon atom. That means in the case of silicon dioxide, it will share 2 of its electrons with another silicon dioxide molecule, just like in aluminum chloride.
150px-Glass_tetrahedon.png
Silicon Dioxide hence has many crystalline forms.
The table below from wikipedia lists them all:
Form
Crystal symmetry
Pearson symbol, group No.
Notes
Structure
α-quartz
rhombohedral (trigonal)
hP9, P3121 No.152[12[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-11|]]]
Helical chains making individual single crystals optically active; α-quartz converts to β-quartz at 846 K
A-quartz.png
A-quartz.png

β-quartz
hexagonal
hP18, P6222, No.180[13[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-12|]]]
closely related to α-quartz (with an Si-O-Si angle of 155°) and optically active; β-quartz converts to β-tridymite at 1140 K
B-quartz.png
B-quartz.png

α-tridymite
orthorhombic
oS24, C2221, No.20[14[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-trid-13|]]]
metastable form under normal pressure
A-tridymite.png
A-tridymite.png

β-tridymite
hexagonal
hP12, P63/mmc, No. 194[14[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-trid-13|]]]
closely related to α-tridymite; β-tridymite converts to β-cristobalite at 2010 K
B-tridymite.png
B-tridymite.png

α-cristobalite
tetragonal
tP12, P41212, No. 92[15[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-14|]]]
metastable form under normal pressure
A-cristobalite.png
A-cristobalite.png

β-cristobalite
cubic
cF104, Fd3m, No.227[16[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-15|]]]
closely related to α-cristobalite; melts at 1978 K
B-cristobalite.png
B-cristobalite.png

faujasite
cubic
cF576, Fd3m, No.227[17[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-16|]]]
sodalite cages connected by hexagonal prisms; 12-membered ring pore opening; faujasite structure.[9[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-fau-8|]]]
Faujasite structure.svg
Faujasite structure.svg

melanophlogite
cubic (cP*, P4232, No.208)[4[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-mel-3|]]] or tetragonal (P42/nbc)[18[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-17|]]]
Si5O10, Si6O12 rings; mineral always found with hydrocarbons in interstitial spaces-a clathrasil[19[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-18|]]]
MelanophlogiteStucture.png
MelanophlogiteStucture.png

keatite
tetragonal
tP36, P41212, No. 92[20[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-19|]]]
Si5O10, Si4O14, Si8O16 rings; synthesised from glassy silica and alkali at 600–900K and 40–400 MPa
Keatite.png
Keatite.png

moganite
monoclinic
mS46, C2/c, No.15[21[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-20|]]]
Si4O8 and Si6O12 rings
Moganite.png
Moganite.png

coesite
monoclinic
mS48, C2/c, No.15[22[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-21|]]]
Si4O8 and Si8O16 rings; 900 K and 3–3.5 GPa
Coesite.png
Coesite.png

stishovite
Tetragonal
tP6, P42/mnm, No.136[23[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-22|]]]
One of the densest (together with seifertite) polymorphs of silica; rutile-like with 6-fold coordinated Si; 7.5–8.5 GPa
Stishovite.png
Stishovite.png

poststishovite
orthorhombic
oP12, Pnc2, No.30[24[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-23|]]]

Poststishovite.png
Poststishovite.png

fibrous
orthorhombic
oI12, Ibam, No.72[25[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-24|]]]
like SiS2 consisting of edge sharing chains
SiS2typeSilica.png
SiS2typeSilica.png

seifertite
orthorhombic
oP, Pbcn[26[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-25|]]]
One of the densest (together with stishovite) polymorphs of silica; is produced at pressures above 40 GPa.[27[[http://en.wikipedia.org/wiki/Silicon_dioxide#cite_note-26|]]]
SeifertiteStructure.png
SeifertiteStructure.png