Transcript NON METALS- SILICON

NON METALS- SILICON
Before we start lets know a
few points..!!
1. Non metals occurs in solid liquid and gaseous states.
2. Non metals are chemically active.
3. All non metals, except graphite, are bad conductors of
electricity.
4. Carbon, sulphur and phosphorous, which are non
metals, exhibit allotropy.
INTRODUCTION
Compounds of silicon in the form of sand, clay,rocks,
etc.
The atomic number silicon: 14
Mass number: 28.
Symbol: Si.
Electronic configuration: 1s2, 2s22p6, 3s2,3p2
How does silicon occurs in nature.?
1. Occurs in the form of oxide.
2. In the form of silicates.
3. In the form of aluminium silicate
4. Silicon is the chief constituent of semi
precious stones like garnet, zircon,
topaz and opal.
topaz
Garnet
zircon
opal
How is silicon Extracted from its
impure form..??
See how its done..!!
https://www.youtube.com/wa
tch?feature=player_detailpag
e&v=B1eO3PCNvDI
Extraction of silicon from quartz..!
1. Finely powdered silica (quartz) is mixed with magnesium
powder and heated in a fire-clay crucible.
2. Magnesium oxide and silicon are formed.
3. The product is washed with dilute hydrochloric acid to
dissolve magnesium oxide.
4. Then it is washed with hydrofluoric acid to remove
unchanged silica.
5. The powder left behind is silicon in its amorphous form.
SiO2 + Mg → Si + 2MgO
Extraction from coke..!
When excess of silica is heated with coke , pale yellow
coloured silicon is obtained in its crystalline form.
SiO2 + 2C → Si + 2CO ↑
PROPERTIES
Physical properties:
1. Amorphous silicon: dark brown coloured powder
insoluble in water. Crystalline silicon forms pale yellow
crystals.
2. Its crystals are hard enough to scratch glass.
3. Melting point: 1683K
4. Boiling point: 2628K.
Chemical Properties
1. Reaction with oxygen: Burns brilliantly in
air and vigorously with O2.
Si + O2 → SiO2
2. Reaction with water: red hot silicon
decomposes steam liberating hydrogen.
Si + 2H2O → SiO2 + 2H2↑
3. Reaction with Carbon: silicon and coke is heated in an
electric furnace to about 3073K, silicon carbide is formed.
Si + C → SiC
SILICON AND ELECTRONICS
At absolute zero temperature it acts as an insulator
At temperature above 300K,covalent bond
breaks free electron and a hole is created
Conductivity of silicon can be
increased by adding impurities.
This process is called “DOPING”.
Adding elements of group 15 to silicon is called n-type
doping.
Adding elements of group 13 to silicon is called p-type
doping.
The silicon is used in making diodes and transistors.
What are the uses of silicon compounds?
1. Quartz glass is used for the manufacture
of threads that are highly elastic which are
used in electrical instruments.
2. Quartz is used in making chemical
apparatus and optical instruments.
3. Sand is used in the manufacture of glass
and porcelain.
4. Sand and stone are used
as building materials.
5. Sodium silicate is called water glass.
Water glass is sodium silicate with excess
of silica. It is used in calico printing.
6. Sodium aluminium silicates are used in softening hard
water.
7. Silicon carbide (SiC) is used as an abrasive for cutting
and grinding glass.
Hope u enjoyed the topic..!!