group 14 elements.ppt

8/10/2019 GROUP 14 ELEMENTS.ppt

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GROUP 14 ELEMENTS



PHYSICAL PROPERTIES

1) ATOMIC SIZE



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



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



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



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



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



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.



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)



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



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



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



When all four oxygen atoms per unit tetrahedron

are shared, a 3D structure formed → quartz



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

group 14 elements.ppt

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