Carlos Francisco
Silicon
Silicon makes up 25.7% of the earth's crust, only being exceeded by
oxygen which can't be as of yet used to create devices out of. In 1800
Davy believed silica to be a compound and not an element. In 1811 Gay
Lussac and Thenard prepared impure amorphous silicon by heating potassium
with silicon tetraflouride. The one credited with the discovery of silicon
though is Jons Berzilius who repeated the 1811 experiment with the same
general method, but he was able to purify it and get silicon where the
others did not. Deville in 1854 became the first to prepare crystalline
silicon.
Silicon is one of the most useful elements to man. It comes in many
forms to accomplish many things. In the form of sand it can be used to
create bricks or concrete or just to have in recreational areas. In forms
of silicates it can be used to make pottery or enamels. Its cheap and one
of the primary ingredients in glass. It is an inexpensive material with
mechanical, optical, thermal and even electrical properties making it very
versatile. It can be used as an insulator. It can be doped with other
minerals to create things such as solar cells, transistors, and other
electronic devices. It is used for computer boards where chips and wires
can be embedded upon it.
Silicon is important in plant and animal life. Diatoms extract silica
from water to build their cell walls. Silica is present in the ashes of
human and plant skeletons. Silicon is an important ingredient in steel and
silicon carbide is an important abrasive and has been used in lasers.
Crystalline silicon has a metallic luster and grayish color. Silicon
is relatively inert, most acids do not affect it. Silicon also transmits
more then 95% of infrared.
Silicon is prepared commercially by heating silica and carbon in an
electric furnace, using carbon electrodes. Silicon is also found free in
nature but it usually occurs as oxides and silica such as sand, quartz,
rock crystal, etc. There are several other methods of creating silicon.
Amorous silicon can be prepared as a powder that can be melted and molded
easily. Another way that could be used is a basic crystal growing method
known as the Czochralski process:
A semi-metal such as silicon is melted in a crucible with an appropriate
amount of dopant, either donor or acceptor. The melting occurs and is
maintained in a partial pressure atmosphere of inert gas, usually argon,
at slightly above the melting point. The heat source is a graphite
resistance heater that surrounds the crucible and is contained within an
insulation layer inside of the furnace.
A seed crystal of the desired orientation is lowered into the liquid and
the temperature is reduced slightly until the liquid begins to crystallize
onto the seed. The seed crystal is then drawn up, slowly at first and then
more quickly, until a long, thin crystal has formed on the end. This is
known as the "neck".
Once the neck has been grown at a sufficient rate and diameter to assure
that it is free of dislocations, the temperature is reduced further and
the growth rate is reduced to allow the crystal to become larger in
diameter. This is known as the "shoulder". As the diameter of the crystal
approaches the desired body diameter, the growth rate is again increased
and temperature is adjusted to create a smooth rounded transition between
the shoulder and body.
This process is used for creating ultra-pure silicon that are wafer
used to build computer boards.
Atomic Number
14
Density
2.33 g/mL
Atomic Weight
28.0855
Melting Point
1685K
Bonding Radius
1.11A
Boiling Point
3540K
Heat of Vaporization
384.22 kJ/mol
Heat of fusion
50.55 kJ/mol
Atomic Radius
1.46A
Specific heat
.71 J/gK
Ionization Potential
8.151 V
Electronegativity
1.9
Silicon is also found in interesting places such as: silly putty, and
breast implants. The structure of silicon is a radius with 14 protons and
neutrons in its shells it has 2 in the inner shell 8 in the next and 4 in
the last shell. There are also 10+ isotopes.