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8/10/2019 GROUP 14 ELEMENTS.ppt
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GROUP 14 ELEMENTS
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PHYSICAL PROPERTIES
1) ATOMIC SIZE
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PHYSICAL PROPERTIES
2) MELTING POINT
C,Si, Ge
giant molecularstructure
strong covalentbond(holding theindividual atoms
together in a threedimension array)
Sn, Pb
giant metallicstructure
melting point Pb
higher than Snbecause Pb more closepacked structure thanSn, although Pb has a
bigger size than Sn
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PHYSICAL PROPERTIES
3) ELECTRICAL CONDUCTIVITY
depends on delocalised electron
C
non-metal(diamond)
it is non-conductor of
electricity
Si, Ge
metalloids
(semiconductor)
Sn, Pb
metals and aregood
conductors ofelectricity
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TETRACHLORIDES AND OXIDES OF GROUP 14
ELEMENTS
All of tetrachlorides of Group 14 elements arecovalent compounds with simple molecularstructures
The atoms of Group 14 undergoes sp3 hybridisation
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VOLATILITY OF TETRACHLORIDE
The intermolecular forces holdingsimple molecular compounds are
weak Van Der Waals forces ofattraction.
All tetrachloride of Group 14elements are volatile liquids with low
melting point and boiling point
Going down the group Van Der Waalsforces of attraction increase
(molecular size increase) hence themelting point and boiling point of the
tetrachloride increase
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THERMAL STABILITY OF TETRACHLORIDE
Going down group 14 the bond length ofM-Cl increase and become weaker
the thermal stability of the tetrachloridesdecreases ( less stable going down thegroup)
CCl4, SiCl4, GeCl4 are stable even at hightemperature
SnCl4 decomposes into SnCl2 when heated at150oC
PbCl4 decomposes into PbCl2 on slightwarming
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H YDROLYSIS OF TETRACHLORIDE
All the tetrachlorides except CCl4 are easilyhydrolysed by water with released of white fumes
of hydrogen chloride
The elements use the empty d orbitals in theouter shell to form dative bonds with watermolecules
Tetrachloromethane CCl4 does not undergohydrolysis because carbon atom has noavailable d orbitals and atomic radius ofcarbon is very small.
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OXIDATION STATE
Group 14 elements form 2 series of oxides with
oxygen:
i. Monoxide MO → +2
- two p-electron are used in bonding- C and Si → covalent ,
Ge → ionic with covalent character,
Sn and Pb → predominantly ionic
ii. Dioxide MO 2 → +4
all 4 valence electrons are used in bonding
(covalent)
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RELATIVE STABILITY OF +2 AND +4 OXIDATION
STATES OF GROUP 14 ELEMENTS
-Oxidation +2 stable for element in the bottom,
oxidation +4 stable for element in the top
Ge4+ (aq) + 2e→ Ge2+ (aq) Eº = -
1.60 V
Sn4+ (aq) + 2e→ Sn2+ (aq) Eº = +0.15 V
Pb4+ (aq) + 2e→ Pb2+ (aq) Eº = +1.69 V
- Eº value more positive ↓ Group the tendency M4+
→ M2+ increases
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Pb2+ is more stable than Pb4+ because of the inert
pair effect
Valence electronic configuration 6s2 6p2
High difference energy level between 6s2 and 6p2 It is difficult for 6s electrons to be promoted to the
6p
Two 6s electrons will remain as an inert pair that
will not be involved in a chemical bonding
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SILICON, SILICONE AND SILICATES
Silicates are compounds containing silicon and oxygen
- The basic init in all silicates is tetrahedral ion, SiO44- Single chain silicate
-When two oxygen atoms per unit tetrahedron are shared to form
single chain → pyroxenes
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When all four oxygen atoms per unit tetrahedron
are shared, a 3D structure formed → quartz
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TIN ALLOYS
Tin is used in the plating of iron / steel container
- Tin is also used in making of alloys
Alloy Composition
Bronze 70% Cu, 30%Sn
Pewter 95% Sn, 3% Cu,
1% Sb
Solder 30% Sn, 70% Pb