[Group 14: C, Si, Ge, Sn, Pb]

Prepared by: Chong Tze Hui

Grace WongChai Jui Jun

CHAPTER 18

Introduction

GROUP 14:

Element Carbon(C)

Silicon(Si)

Germanium(Ge)

Tin(Sn) Lead(Pb)

Proton number

6 14 32 50 82

Electronicconfiguration

2.4 2.8.4 2.8.18.4 2.8.18.18.4

2.8.18.32.18.4

-They are known as the p-block elements.

carbon, C [He]2s22p2

silicon ,Si [Ne]3s23p2

germanium,Ge [Ar]3d104s2 4p2

tin, Sn [Kr]4d105s2 5p2

LEAD ,P [XE]4F14 5D106S2 6P2

b

Physical Propertie

s

ATOMIC RADIUS

C The nuclear charge and screening effect increases. Si Screening effect increases faster than

nuclear charge.Ge This causes the effective nuclear charge to

decrease and the size of the atoms to

Sn increases.

Pb

Increases

C Si Ge Sn Pb

FIRST IONISATION ENERGY

First ionisation energy/kJ mol‾

X

X

X

X X

1

Proton number

C

Si

Ge

Sn Pb

-First ionisation energy when descending the group,becausethe in the effective nuclear charge,The valence electrons are easy to remove.-Pb is slightly higher than Sn,this is due to the ineffective screening by the f electrons in the Pb.In fact,there is a slight decrease in the screening effect from Sn to Pb.

MELTING POINT

Element C Si Ge Sn Pb

Melting Point/ºc

3730 1410 937 232 327

Structure Giant covalent molecule giant metallic

- Because the atomic saiz of Ge > Si > C, the strength of the covalent bond in the lattice in the order C > Si > Ge. Therefore, the melting point from C to Ge.

Lead are arranged according to face-centred cubic structure(Closely-packed) .

The atoms follow a tetragonal structured arrangement which is more open.

This causes the melting point of lead to be higher than tin.

ELECTRIC CONDUCTIVITY

C Si Ge Sn Pb

INCREASE

This corresponds with the properties of the elements which changes from non-metals to metal.

C Non-conductor(except for graphite)Si & Ge Semi-conductor Sn & Pb Conductors

Chemical Properties

OXIDATION STATES OF +2 & +4

Elements Oxidation number

C +2, +4

Si +4

Ge +4

Sn +2, +4

Pb +2, +4

The stable oxidation number is in hold.

The elements of Group 14 from two oxidation states: +2 & +4.

RELATIVE STABILITY OF THE +2 &+4 OXIDATION STATE

The +4 oxidation state involves the promotion of an s electron to an empty p orbital.

Energyabsorbed

Energy

+2 State +4 State

Pb with big proton number is less likely to use two electrons from the s orbital to be shared. This is called the inert pair effect.

The in the atomic size when going down the group causes the covalent bonds to become weaker.Therefore, the energy released when the two covalent bonds are formed is not enough to “excite” the s electrons to promote it to the f orbitals in the case of lead.

proton number C Si Ge Sn Pb

--------------------------

+2

+4

Relative stability

a. Ge (aq) +2e Ge (aq) E = -1.60Vb. Sn (aq) + 2e Sn (aq) E = +0.15Vc. Pb (aq) + 2e Pb (aq) E = +1.80V

As the E values become increasingly positive going down

the group,the tendency for the M state to get converted

to the M state increases.

4+

4+

4+

2+

2+

2+

Ø

4+

2+

ø

ø

ø

Example:Carbon monoxide is a reducing agent because the +4 oxidation state is more stable. In industries , carbon monoxide is used in the extraction of iron from its ore.

Fe2O3(s)+ 3CO(g) →2Fe(s) + 3CO2(g)

Carbon monoxide is oxidised to carbon dioxide.

For Tin, the +4 oxidation state is slightly more stable than the +2 oxidation state.Aqueous tin(II)ions are weak reducing agent.

Example: it can reduce iron(III) salt solution to iron (II).

Sn (aq)+ 2Fe (aq) → 2Fe (aq) + Sn (aq)

Lead(IV)oxide is a strong oxidising agent.

PbO2(s)+4HCl(aq)→PbCl2(s)+ Cl2(g)+ 2H2O(l)

2+ 3+ 2+ 4+

TETRACHLORIDES OF GROUP 14

All elements in Group 14 forms Tetrachloride compounds.(XCl4)

The X-Cl bond is a covalent bond and the intermolecular forces of attraction between the tetrachloride molecules is the weak van der waals forces.

X

Cl

ClCl

Cl

109.5°

Exist as simple MCl₄ molecule with a tetrahedral shape.

Prepared by passing dry chlorine gas into liquid carbon disulphide and boiling under reflux ,iodine as cataylst.

Germanium tetrachlorides-Ge(s)+2Cl₂ (l)→GeCl₄ (l)

Silicon tetrachlorides-Si(s)+ 2Cl₂(l)→SiCl ₄(l)

Tin tetrachlorides-Sn(s)+2Cl →SnCl (l)

Lead tetrachlorides- prepare with cool lead+concentrated HCl to prevent

the decomposition- Pb(s)+4HCl(aq)→PbCl ₄ (l)+2H₂ (g)

PHYSICAL PROPERTIES OF THE TETRACHLORIDESTetrachlorides *CCl₄ SiCl₄ GeCl₄ SnCl₄ PbCl₄

Melting point/ºC -23 -70 -50 -33 -15

Boiling point/ºC 77 59 86 114

decompose

Strenght of the van der Waals forces increasing,melting point and boiling point increasing

THERMAL STABILITY OF TETRACHLORIDES

X-Cl bond weak. Thermal stability decrease.

CCl₄ SiCl₄ ,and GeCl₄ are stable at high temp. SnCl₄decompose on heating SnCl₄ (l)→SnCl ₂ +Cl₂ (g)

tin(П)chloride PbCl₄decompose on slight warming PbCl₄(l)→PbCl₂+Cl₂(g)

lead (П) chloride

decreasing

Hyrolysis of the tetrachlorides

XCl₄(l)+2H₂O(l) →XO₂(s)+4HCl(aq)

All tetrachlorides (except CCl₄) are hyrolysed by water.

Si,Ge,Sn and Pb’s empty d orbitals respective to Cl to form coordinate (dative) bond with water molecule.

Mechanism for the hydrolysis of SiCl₄

si

HClHCl

HClHCl

O

O

Elemnt C Si Ge Sn Pb

Monoxide CO SiO GeO SnO PbO

Dioxide CO₂ SiO2 GeO₂ SnO₂ PbO₂

Oxides of group 14:

All oxides formed by Group 14 elements are of two types:(a)Monoxides, XO with an oxidation state of +2 for its element.(b)Dioxides,XO2 with an oxidation state of +4 for its element.

Monoxides: For the Group 14 elements at the top of the

group, the oxidation state of +2 is unstable compared to the oxidation state of +4. Hence, the monoxides of C, Si, Ge, & Sn are easily oxidised upon heating.

Monoxide

CO SiO GeO SnO PbO

Structure

Simple molecule Primary ionic

Physicalstate Gas Gas* Solid

Thermalstability Convert to dioxide Stable

Acid/Basenature

Natural Amphoteric( *SiO) exists as a gas only at temp. above 2000ºC

(A)THERMAL STABILITYOF THE MONOXIDES

CO -is a gsa under room conditions,-burns with blue flame in air form CO₂-slowly get oxidised to dioxide when exposed

to air2CO(g) +O₂(g)→2CO₂(g)

SiO-only exists in gas phase at temp. above

2000ºC-it changes spontaneously to dioxide when

cooled 2SiO (g) → SiO₂(s)+ Si (s)

GeO,SnO-readily oxidised to dioxide when left

composed to air(a) 2GeO(s) +O₂ (g) → 2GeO₂ (s)(b) 2Sn (s) + O₂(g) → 2SnO₂ (s)

PbO - stable on heat -heating at temp. above 400ºC,it get

converted to Triplumbum tetraoxide,Pb₃O₄ 400°c6PbO(s) + O₂(g) 2Pb₃O₄(s) yellow 470°c orange/brown

(B) THE ACID/BASE NATURE OF THE MONOXIDES

CO and SiO are neutral- sodium methanoate is formed when CO is

bubbled through concentrated sodium hyroxide at 200ºC.

CO(g) +NaOH (aq) → HCOONa (aq) GeO,SnO and PbO are amphoteric.(a)They react with dilute acids to form salts.

MO(s) +2H⁺ (aq) → M²⁺ (aq) +H₂O (l)(b) They react with hot and dilute alkali to form

salts. MO(s) +2OH⁻(aq)+HO (l)→M(OH)₄²⁻

DIOXIDE OF THE GROUP 14 ELEMENT

Dioxide CO₂ SiO₂ GeO₂ SnO₂ PbO₂

Structure

Simple molecule Primary ionic

PhysicalState Gas Solid

ThermalStability Stable

Decompose to PbO

Acid/BaseNature

Acidic Amphoteric

(A) THERMAL STABILITY

CO₂ , SiO₂ , GeO₂ and SnO₂ stable to heat. Lead (IV)oxide decompose on heating to form lead (II) oxide.2PbO₂(s) →2PbO(s) + O₂(g)

(B)ACID/BASE NATURE OF THE DIOXIDES

CO₂ and SiO₂ are acidic. Carbon dioxide react with dilute sodiun

hydroxide form carbonate.CO₂(g) +2NaOH(aq)→ Na₂CO₃(aq) +

H₂O(l) Silicon dioxide dissolves in hot and

concentrated sodium hydroxide form silicate.SiO₂(s) + 2NaOH (aq) → Na₂CO₃(aq) +

H₂O (l) Silicon dioxide is also soluble in concentrated

hydrofluoric acid,HF. SiO₂(s) + 6HF (aq) →[SiF₆]²⁻+2H⁺(aq)+2H₂O(l)

GeO₂,SnO₂ and PbO₂ are amphoterica.)Reaction with acid(react with hot and

concentrated hyrochloric acid to form salts)GeO₂ (s)+4HCl(aq) → GeCl₄(l) +

2H₂O(l)SnO₂(s) + 4HCl (aq)→ SnCl₄(l) + 2H₂O(l)

-lead dioxide react with hot and concentrated hyrochloric acid →lead (II) chloride and chlorine gasPbO₂(s)+4HCl(aq) → PbCl₂(s)+Cl₂(g)+ 2H₂O(l)

- lead dioxide react with cold <20ºC and concentrated hyrochloric acid →lead (IV) chloride PbO₂(s)+4HCl(aq) → PbCl₄(s) + 2H₂O(l)-lead (IV) chlorided decompose slowly at room temp.to lead (II) chloride

b.)Reaction with alkali -GeO₂ , SnO₂ ,and PbO₂ react with hot and concentrated sodiun hydroxide→

germanate(IV) GeO₂(s)+2NaOH(aq)+2H₂O(l)→Na₂Ge(OH)₆(aq)

stanate(IV)SnO₂(s) +2NaOH(aq)+2H₂O(l)→Na₂Sn(OH)₆(aq)

plumbate(IV)PbO₂(s) +2NaOH(aq)+2H₂O(l)→Na₂Pb(OH)₆(aq)

CATENATION

Ability of an element to form bonds between atoms of the same element

—C—C—C—C—C—M-M bond C—C Si—Si Ge—Ge Sn—Sn C=C CΞC

Bond energy/kJmol⁻¹

348 176 188 150 610 840

Carbon has strongest M-M bonds,strong double and triped bonds

Only Carbon can cantention to form a series of compound(organic compounds)

USE OF CARBON

Common Uses of Carbon Used as a decorative tool in jewelry items. Used as a base for the ink that is used in

inkjet printers. Used in the rims of automobiles as a black

fume pigment. Vegetal carbon, is sometimes used as a

bleaching agent or a gas absorbent. Carbon (in the form of carbon dioxide) is also

used in carbonated and fizzy drinks, fire extinguishers, and also as dry ice when they are in a solid state.

In metallurgy, carbon monoxide is also utilized as a reduction agent in order to derive many other elements and compounds.

Carbon in the form of 'Freon' is also used in cooling devices and systems.

Many metal cutters and heat resistant tools and devices are also manufactured with carbon.

Some allotropes of carbon: a) diamond; b) graphite; c) lonsdaleite; d–f) fullerenes (C60, C540, C70); g) amorphous carbon; h) carbon nanotube.

USES OF CARBON ELEMENT - GRAPHITE

one of the allotropes of carbon that out of all the materials that are found in

nature, graphite is one of the softest substances.

primary uses of graphite:1. Used as a lubricant.2. Used as lead in pencils.3. In the form of coke, used in the production

process of steel.

PRODUCT OF CARBON-GRAPHITE

USES OF CARBON ELEMENT - DIAMOND

Making of high speed drilling materials and precious stone.

-Diamond bearing are used in instruments for laboratoties.

-Diamond cutting tools cut much faster and accurately than other tools. Metals can be sliced thinner than human hair by the diamond blade.

Products of diamonds

USES OF TIN

3.used in solder,tin plating, tin chemicals, brass and bronze, and other.

Solder Tin-Antimony1. High temperature and food industry

applications2. Non-toxic. 3. Good high temperature properties. 4. Better electrical conductivity and strength

than tin-lead solders. 5. Good wetting.

1.Tin is extracted from the cassiterite ore (SnO₂) .2.SnO₂ is reduced to tin by carbon at 1200-1300°C in an electrical furnace.

Pewter plateInside of a tin platted can

Product of Tin

Tin-Antimony-Lead1. Suitable fo joining copper/other alloy metals2. Improved mechanical properties over Tin-

Lead solders. 3. Can not be used with zinc due to brittle

zinc-antimony inter-metallic compounds Tin-lead1. General purpose, and the most widely used

solders. 2. Good process characteristics and the best

understood solders.

Tin-Silver1. Used for soldering medical or high precision

instruments. 2. High temperature applications3. Non-toxic but expensive. Good high

temperature properties.

USES OF SILICON essentially a semi-metal (has some metallic

properties such as metallic conductivity) that allows it to be used in semi-conductor devices (i.e., silicon is a semiconductor).

Making silicane(an organosilicon polymer)used as lubricants,hydraulic fluids ,car polish,electric insulator,water-proof fabric, elastomers, resin, grease,and resinous materials.

Strucuture of Silicone

Strucuture of Silicone

Polyester Resin for Hybrid Powder Coating

silicone

A mobile phone case made from silicone

A silicone rubber hose

SILICON(IV)OXIDE OR SLILICA

SRUCTURE OF SILICA

• Repeating unit in silicon(IV)oxides is the tetrahedral “SiO₄”

Chemical Properties Of

Silicon (IV) Oxide

Silicon(IV) oxide is chermically inert. Only attacked by:1. hydrofluoric acid →hexafluoric acid SiO₂(s)+6HF(aq) → 2H⁺(aq)+[SiF₆]²⁻(aq)

+2H₂O(l)2. concentrated alkalis→silicate

SiO₂(s) +2NaOH(aq) →Na₂SiO₃(aq) +H₂O(l)

USED OF SILICA , SILICON(IV) OXIDE

Quart or sand―glass and lenses for optical

instrument.―important component in electronic

such as radar. Silica--(sand) is used extensively in making cement,

concrete and ceramics.

EXTRACTION OF PHOSPHOROUS

The pentoxide reduced by coke to phophorousP₂O₅+3C →2P +5CO

Used in the anhhydrite process to eliminate sulphur dioxide.SiO₂(s) +3C(s) ―→ SiC(s) +2CO(g)

silicon carbide

There are three naturally occuring crystalline forms of silicon(IV) oxide.

The most stable form of silicon(IV) oxide at room condition is quartz. Sand is powdered quartz contaiminated with iron(III) oxide.

Quartz

870ºC

Tridymite

cristobalite

1470ºC

GLASS

-When silica is heated at around 1710°C,silicate glass (or quartz glass) is formed.

-Quartz glass are transparent to infrared and ultraviolet radiations.

Quartz glass

Soda-lime Glass

Potash Glass

Borosilicate glass

Aluminosilicate Glass

SILICATE

Silicates When silicon(IV)oxide(silica) reacts with a molten base, silicates are formed.The basic building block of all silicates is the SiO⁴¯₄.

Silicates with discrete SiO₄⁴⁺ ions.- simple silicates such as Mg₂SiO ₄, ZrSiO ₄ contain SiO₄⁴⁺

ions.

Aluminosilicate

When Si⁴⁺ ions are replaced by Al³⁺ions, aluminosilicates are formed.

To maintain electrical neutrality, another cation, e.g.; Na⁺, K⁺ or Ca²⁺, must be incorporated.

History

Carbon Carbon was known in prehistory in the form

of soot; while charcoal was made in Roman times (by heating wood while exclude air) and diamonds were known as early as 2500 BC in China. In 1772, Antoine Lavoisier showed that diamonds were a form of carbon, when he burned samples of carbon and diamond and showed that both formed the same amount of carbon dioxide per gram of material. Carl Scheele showed that graphite was a form of carbon rather a form of lead.

Figure 1: French chemist and biologist Antoine-Laurent de Lavoisier (1743 – 1794).

Figure 2: German-Swedish pharmaceutical chemist Carl Wilhelm Scheele (1742 - 1786). Author Isaac Asimov has called him "hard-luck Scheele" because he made a number of chemical discoveries before others who are generally given the credit

A new allotrope of carbon, fullerene, was discovered in 1985 by Robert Curl, Harry Kroto, and Richard Smalley who subsequently shared the Nobel Prize in Chemistry in 1996. Fullerenes have been reveled to include nanostructured forms such as buckyballs and nanotubes. The renewed interest in new forms lead to the discovery of further exotic allotropes, including glassy carbon, and the realization that amorphous carbon is not amorphous.

SILICON

Silicon was first identified by Antoine Lavoisier in 1787 as a component of flints, and was later mistaken by Humphry Davy for a compound rather than an element. In 1824, Berzelius prepared amorphous silicon by the reaction of potassium with silicon tetrafluoride.

Figure 4: British chemist and inventor Sir Humphry Davy FRS (1778 - 1829).

Figure 5: Swedish chemist Jöns Jacob Berzelius (1779 – 1848).

Germanium is one of three elements the existence of which was predicted in 1871 by the Russian chemist Dmitri Mendeleev when he first devised his periodic table. Not until 1886, however, was germanium identified as one of the elements in a newly found mineral.

Dmitri Mendeleev

The origins of tin seem to be lost in history. It appears that bronzes, which are alloys of copper and tin, were used by prehistoric man some time before the pure metal was isolated.

Lead is mentioned often in early Biblical accounts. The Babylonians used the metal as plates on which to record inscriptions. The Romans used it for tablets, water pipes, coins, and even cooking utensils; indeed, as a result of the last use, lead poisoning was recognized in the time of Augustus Caesar. The compound known as white lead was apparently prepared as a decorative pigment at least as early as 200 BCE. Modern developments date to the exploitation in the late 1700s of deposits in the Missouri–Kansas–Oklahoma area in the United States.

End

QUESTION:

[Q2 Paper(2A)STPM 2000] 1.a)The tetrachlorides of Group 14 elements,

i.e. CCl₄, SiCl₄, GeCl₄, SnCl₄ and PbCl₄ are liquids at room temperature. All the tetrachlorides, with the exception of CCl₄, are hydrolysed i n aqueous solution to form acidic solutions.

i) State the molecular shape of all the Group 14 tetrachlorides.

ii) Write a balanced eq. for the hydrolysis of SiCl₄.

iii) Explain why CCl₄ does not undergo hydrolysis. [4]

b) The standard electrode potentials,at 298K, for some half-cells are given below.

Half-cell E° / V

Ge⁴⁺(aq)+2e Ge⁴⁺(aq) -1.60

Sn⁴⁺(aq) +2e Sn²⁺(aq) +0.15

Pb⁴⁺(aq) +2e Pb²⁺(aq) +1.80

i)Arrange the Ge⁴ ion, Sn⁴ ion and Pb⁴ ion in the order of ⁺ ⁺ ⁺decreasing stability in aqueous solution.ii)Which ion has the most powerful reducing property?iii)Which is more stable in aqueous solution, Pb² or Pb⁴ ? ⁺ ⁺Explain your answer.[4]

STPM 2005/P2/Q7 A scheme of reaction is shown below. X(l) Y(s)+Cl₂(g)

HCl(aq)

  Tetrachloroplumbate(ll)(aq) ion

Identify compound X and discuss its chemical properties.

Compound X is an oily liquid while compound Y is a white solid. Explain the different physical states of the two compounds.

Answers: [Q2 Paper(2A)STPM 2000]1.a)i) Tetrahedron ii) SiCl₄(l)+2H₂O(l)→SiO₂(s)+ 4HCl(aq) iii)C is an element in period 2 of the periodic

table. It does not empty orbitals in its valence shell (n=2 )to form co-ordinate bonds with water molecules.

b)i) Stability: Ge⁴⁺> Sn⁴⁺> Pb⁴⁺ii)Ge²⁺iii)Pb²⁺

STPM 2005/P2/Q71.a)X is PbCl₄, lead(IV)chloride. X is thermally unstable and will

decompose on heating. Pb⁴⁺has strong oxidizing power.b)X is a covalent compound with weak van der

waals forces of attraction. Y (PbCl₂)is an ionic compound with strong

ionic bonds between Pb²⁺ion and Cl‾ ions.