The P-Block Elements

The elements of the group 13 – 18 come under the p – block elements. In these elements the last electron enters in the outermost p – orbital. They have ns2np1-6 electronic configuration in valence shell, helium being an exception. These elements show the maximum oxidation state equal to the sum of electrons in the outermost shell or valence shell. Most of the elements of the p – block form covalent compounds although some elements form ionic compounds (such as halogens) and coordination compounds as well. p-block contains elements which are either metals, non – metals or metalloids. p-block elements include the group of halogens and inert gases. First member of each family of the p-block elements is given below in the table with their general electronic configuration and oxidation states. p-block has the most electronegative element which is fluorine. Elements of p-block generally form acidic oxides. Many elements such as C, Si, Ge, O, N etc. also show phenomena of allotropy. Property of catenation is also shown by many elements.  


Group 

13

14

15

16

17

18

First Member of the Group

He

General Electronic Configuration 

ns2np1

ns2np2

ns2np3

ns2np4

ns2np5

ns2np6

Group Oxidation State 

+3

+4

+5

+6

+7

+8


Group 13 Elements: The Boron Family 

Group 13 is the first group of p-block elements. First element of this group is Boron which is the only metalloid of this group. This is the reason that group 13 is also known as boron family.  


Elements of the Group - 13

Atomic Number 

Symbol 

Metal/non-metal/metalloid

Color 

Electronic Configuration 

Density g/cm3 at 298 K

Atomic and Ionic Radii 

Ionization Enthalpy 

5

Metalloid 

Black brown color

[He] 2s2 2p1

2.35

Increases on moving from top to bottom in the group

(Exception – Atomic radium of Ga is less than Al)

Decreases on moving from top to bottom in the group (Exception – Ga and Tl show higher ionization enthalpies)

13

Al 

Metal 

Silver or grey color

[Ne] 3s2 3p1

2.70

31

Ga

Metal 

Silvery blue color

[Ar] 3d10 4s2 4p1

5.90

49

In 

Metal

Silvery white color

[Kr] 4d10 5s1 5p1

7.31

81

Tl 

Metal

Silver white color 

[Xe] 4f14 5d10 6s2 6p1

11.85



Elements of the Group 13 – Physical Properties 

Symbol 

Atomic Number 

Atomic Mass (g mol-1)

Melting Point (K)

Boiling Point (K)

Density 

Ionic Radius 

5

10.81 

2453

Decreases on moving from top to bottom in the group, although Ga has exceptionally low m.p. 

3923

Decreases on moving from top to bottom in the group

Increases on moving from top to bottom in the group (Exception – K-shows lower density)

Increases on moving from top to bottom in the group

Al 

13

26.98

933

2740

Ga

31

69.72

303

2676

In 

49

114.82

430

2353

Tl 

81

204.38

576

1730


Elements of the Group 13 – Chemical Properties

Oxidation Number 

B does not show +3 oxidation state and forms only covalent compounds due to its small size and high ionization enthalpies.

Al shows +3 oxidation state while Ga, In and Tl show both +1 and +3 oxidation states. 

As we move down in the group towards the heavier metals, +1 oxidation state dominates. 

Tendency to behave as Lewis Acid 

The tendency to behave as Lewis acids of group 13 elements decreases on moving down the group due to increase in the size of atom. 

-

-

Reactivity towards Air 

Group 13 elements react with oxygen in the air and form respective oxides. 

2A + 3O2 🡪 2A2O3

These elements react with nitrogen in the air and form nitrides. 

2A + N2 🡪 2AN

(where A = element of group 13) 

The nature of oxides of group 13 elements vary on moving down the group. 

Boron trioxide – Acidic 

Oxides of Al and Ga – Amphoteric 

Oxides of In and Tl – Basic 

Reactivity with Acids 

Boron does not react with acids. 

Aluminum reacts with mineral acids. 

Reaction of Al with dilute HCl –

2Al + 6HCl 🡪 2AlCl3 + 3H2

Reactivity with Bases 

Boron does not react with alkalies (bases which are soluble in water)

Al is amphoteric in nature and reacts with alkalies as well. 

Reaction of Al with NaOH –

2Al + 2NaOH + 6H2O 🡪 2NaAl(OH)4 + 3H2

Reaction with Halogens 

All elements of group 13 react with halogens. 

The elements react with halogens and form trihalides. 

2A + 3X2 🡪 2AX3

Exception – TlI3 does not exist due to its unstable nature. Tl forms stable compounds at +1 oxidation state. 


Important Trends and Anomalous properties of Boron 

Important trends of group 13 elements are listed below –

  • Trichloride, Tribromides and Triiodides of group 13 elements are covalent in nature and can be hydrolyzed in water. 

  • Monomeric trihalides of these elements are strong Lewis acids. 

BF3 + :NH3 🡪 NH3-BF3

  • Metal halides of group 13 elements are generally dimerized through halogen bonding. 

Anomalous properties of Boron are listed below –

  • Boron shows quite higher melting and boiling points than other elements of group 13. 

  • Boron forms only covalent compounds while other elements of the group 13 form both ionic and covalent compounds. 

  • Boron is a metalloid while other elements of the group 13 are metals. 

  • Oxides and hydroxides of boron are acidic in nature while oxides and hydroxides of other elements of the group are amphoteric and basic in nature. 


Some important Compounds of Boron 

Compounds of Boron 

Preparation/ Discovery  

Properties 

Uses 

Borax 

IUPAC name – Sodium Tetraborate Decahydrate 

Chemical formula – 

Na2B4O7.10H2O

(or Na2[B4O5 (OH)4].8H2O)

Borax was discovered in Tibet in the dry lake beds. 

  • It is a white crystalline solid. 

  • It dissolves in water and forms an alkaline solution. 

Na2B4O7 + 7H2O 🡪 2NaOH + 4H3BO3

  • On heating it forms borax beads. 


  • Borax beads are used in borax beads test to identify transition elements in laboratories. 

Orthoboric Acid 

IUPAC name – Trihydrooxidoboron or Boric acid

Chemical Formula – H3BO3

By acidifying aqueous solution of borax – Orthoboric acid can be prepared by reaction of aqueous solution of borax and acid. 

Na2B4O7 + 2HCl + 5H2O 🡪 2NaCl + 4B(OH)3


  • White crystalline solid with soapy texture. 

  • It is slightly soluble in cold water but high soluble in hot water.

  • It is a weak monobasic acid. 

  • It acts as a Lewis acid. 

  • On heating at 370 K temperature, it gives metaboric acid (HBO2). 

  • On heating metaboric acid gives boric oxide (B2O3).  

  • Used in manufacturing of fiberglass. 

  • Used in the jewelry industry. 

  • Used in LCD flat panels.

  • Used as an antiseptic. 

  • Used to control termites, ants etc. 

  • It destroys wet and dry rot in timbers. 

Diborane (IUPAC name)

Common name – Diboron Hexahydride 

Chemical formula – B2H6


  • It is prepared by the reaction of boron trifluoride with lithium aluminium hydride in diethyl ether. 

4BF3 + 3LiAlH4 🡪 2B2H6 + 3LiF + 3AlF3

  • Laboratory method – by oxidation reaction of sodium borohydride with iodine. 

2NaBH4 + I2 🡪 B2H6 + 2NaI + H2

  • Industrial method – by the reaction of boron trifluoride with sodium hydride at 450 K temperature. 

2BF3 + 6NaH 🡪 B2H6 + 6NaF

  • It is a colorless gaseous compound. 

  • It is a highly toxic gas.

  • Its boiling point is 180 K. 

  • It catches fire immediately on exposure to air. 

  • It burns with a large amount of energy. 

  • It easily gets hydrolyzed by water and gives boric acid.

B2H6 + 6H2O 🡪 2B(OH)3 + 6H2

  •  It shows cleavage reactions with Lewis bases. 

  • It reacts with ammonia and gives borazine which is called ‘inorganic benzene’. 

  • Used as rocket propellant. 

  • Used as a rubber vulcanizer. 

  • It is used as a catalyst for polymerization of hydrocarbon. 

  • Used as an accelerator for flame speed. 

  • Used in production of semiconductors. 

  • Used in production of highly pure boron. 


Uses of Boron and Aluminium and their Compounds

Boron, aluminium and their compounds are of great importance biologically and environmentally. Few of their applications are listed below –

  • Boron fibers are used in the bullet proof jackets. 

  • Boron is used in light composite material for aircrafts. 

  • Boron compounds are used in glass making, borax beads test, jewelry industry, antiseptic. 

  • Various boron compounds are used as rubber vulcanizer, rocket propellant, flame speed accelerator etc. 

  • Aluminium is used in wires as it’s a good conductor of electricity. 

  • Al is used in various utensils as well as it’s a good conductor of heat. 

  • It is used in pipes, rods, tubes etc. 

  • Al is used in many alloys of Zn, Mg, Cu, Mn etc. 

  • Compounds of aluminium are used in manufacturing of rubber, pharmaceuticals, textiles and as pesticides, lubricants and wood preservatives. 

  • Al compounds are used in preparation of many compounds. 

  • Aluminium chloride is used as a catalyst in Friedel - Craft acylation reaction.

 

Group 14 Elements: The Carbon Family 

Group 14 is the second group of p-block elements. First element of this group is carbon which is found in large quantities in nature and the 7th most abundant element in the earth’s crust. This is the reason that group 14 is also known as carbon family. Apart from this carbon also shows various unique properties as well such as catenation etc. The branch of chemistry – Organic Chemistry is based on the carbon and its compounds. 


Elements of the Group - 14

Atomic Number 

Symbol 

Metal/Non-metal/Metalloid

Color 

Electronic Configuration 

Density g/cm3 at 298 K

Covalent and Ionic Radii 

Ionization Enthalpy 

6

Non – metal 

Black, clear transparent 

[He] 2s2 2p2

3.51 

Increases on moving from top to bottom in the group


Decreases on moving from top to bottom in the group (Exception –Lead which possess higher ionization enthalpy than tin)

14

Si 

Metalloid

Bluish black 

[Ne] 3s2 3p2

2.34

32

Ge 

Metalloid

Greyish white 

[Ar] 3d10 4s2 4p2

5.32

50

Sn 

Metal

Silvery white color

[Kr] 4d10 5s2 5p2

7.26

82

Pb 

Metal

Metallic gray 

[Xe] 4f14 5d10 6s2 6p2

11.34 


Elements of the Group 14 – Physical Properties 

Symbol 

Atomic Number 

Atomic mass (g mol-1)

Electronegativity 

Melting Point (K)

Boiling Point (K)

Density 

Ionic Radius 

6

12 

All elements of group 14 from silicon to lead have the same electronegativity. Although electronegativity of group 14 elements is slightly more than group 13 elements due to their smaller size. 

4373

Decreases on moving from top to bottom in the group, although Pb has exceptionally high m.p. 

-

Decreases on moving from top to bottom in the group

Increases on moving from top to bottom in the group (Exception – Si possess exceptionally low density)

Increases on moving from top to bottom in the group

Si 

14

28 

1693

3550

Ge 

32

72.60 

1218

3123 

Sn 

50

118.71 

505

2896

Pb 

82

207.2

600

2024


Elements of the Group 14 – Chemical Properties

Oxidation States 

Elements of group 14 exhibit +4 and +2 oxidation states. 

Carbon shows +4 oxidation state. 

Tendency of showing +2 oxidation state increases on moving down the group. 

Ge, Sn and Pb show +2 oxidation state. 

Reaction with Oxygen 

All elements of group 14 reacts with oxygen and form oxides. 

These elements form monoxide and dioxides. 

Examples – CO2, SiO2, GeO, SnO, PbO. 

Reaction with Water 

In group 14, tin is the only element which reacts with water. All other elements remain unaffected by water. 

Sn + 2H2O 🡪 SnO2 + 2H2

Lead remain unaffected by water due to the formation of a layer of an oxide on its surface. 

Reaction with halogens 

All elements of group 14 (except carbon) react with halogens directly and form halides. 

These elements form MX2 or MX4 type halides. 

Heavier elements form MX2 type halides. While lighter elements form MX4 type halides. 

Tetrahalides (MX4) are covalent in nature. In these molecules the central metal atom is sp3 hybridized and tetrahedral in shape. 

Except CCl4, all other tetrachlorides of these elements can be easily hydrolyzed.

SinCl4 + 4H2O 🡪 Si(OH)4 + 4HCl 

Hydrides 

All group 14 elements form hydrides. 

These elements form EH4 or E2H6 type hydrides. (where E = any one element of group 14)

EH4 – CH4, SiH4, GeH4, SnH4, PbH4

E2H6 - C2H6, Si2H6, Ge2H6, Sn2H6

Carbon forms alkane, alkene and alkyne as hydrides. 

Catenation 

Catenation is the property of elements to bind itself through covalent bonds to form chain and ring compounds. 

Carbon shows the property of catenation and forms many compounds. 

The tendency to show catenation decreases as we move down the group due to increase in size and decrease in electronegativity. 


Important trends and Anomalous behavior of Carbon 

Carbon differs from other members of the group 14. This is because of small size of carbon atom, higher electronegativity, higher ionization enthalpy, unavailability of the d-orbital and catenation property of carbon. 

In carbon d – orbital is not available for bonding, only s and p orbitals are available for bonding. This is the reason it can accommodate only 4 pairs of electrons in bonding. 

Carbon can form multiple bonds with another carbon atom and other atoms of other elements which possess high electronegativity and small size. For example, C=C, C=O, C=N etc. Carbon can form chain and ring compounds. It shows the property of catenation. 

Many allotropes of carbon are found in nature due to its catenation property.

 

Allotropes of Carbon 

Many crystalline and amorphous allotropic forms of carbon are found in nature. The property of elements to exist in two or more different forms is called allotropy and the different forms are called allotropes of that element. Here, we are discussing three main allotropes of carbon in the table given below –

Allotropes of Carbon and their Properties 

Diamond 

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Pic-1

  • Diamond is a crystalline allotropic form of carbon. 

  • In diamond each carbon atom is sp3 hybridized and bonded with 4 other carbon atoms. 

  • It is a transparent, shiny substance. 

In diamond carbon atoms are bonded by single covalent bonds. 

Diamond is the naturally occurring hardest substance on earth. 

Diamond is used in ornaments, glass cutting, dyes making, manufacturing of tungsten filament etc. 

Graphite 

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Pic-2

Graphite is iron-black to steel – gray colored another allotropic form of carbon. It is not as hard as diamond. 

It is found in amorphous, crystalline and lumpy forms. 


It has a layered structure and these layers are linked together by van der Waals forces. 

The layers are separated by the distance of 340 pm.  

Each layer is composed of planar hexagonal rings of carbon. 

The C-C bond length in the hexagon ring is 141.5 pm. 

Each carbon atom is sp2 hybridized and bonded with 3 carbon atoms by sigma bond in the hexagon ring. 

In graphite electrons can move in the layer so it is a conductor of electricity. 

As layers in the graphite are present at a distance so it is very soft and slippery. 

It is used as a lubricant. It is also used in batteries, steelmaking, brake linings, pencils etc.  

Fullerenes 

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Fullerenes were discovered by H. W. Kroto, E. Smalley and R.F. Curl. 

Fullerenes are cage-like molecules in which carbon atoms are bonded together by single or double bonds. It is also an allotrope of carbon. 


They are made on heating graphite in an electric arc in the presence of inert gases such as He, Ne etc. 

Spherical fullerenes are called bucky balls. 

Fullerenes generally contain C60 or C70 molecules. Although fullerenes containing up to 350 carbon atoms have also been found. 

C60 fullerene is called buckminsterfullerene. It has a soccer ball like structure. 

It has 20 six membered rings and 12 five membered rings. A six membered ring can link with either five membered rings or six membered rings while a five membered ring can link only to a six membered ring. 

It possesses aromatic character and has 60 vertices. 

Single C-C bond length is 143.5 pm and double C-C bond length is 138.3 pm in buckminsterfullerene. 

Fullerenes are used in drug delivery in the body, lubricants and catalysts. 

Graphite is the most stable allotrope of carbon thermally. 

Carbon black, coke and charcoal are all impure forms of graphite and fullerene. 


Uses of Carbon 

Carbon is a very useful element. Organic chemistry is based on carbon and its compounds. Few of its uses are listed below – 

  • Graphite is used in batteries and filaments due to its electricity conducting property. 

  • Diamond is used in glass cutting. 

  • Graphite is used in the pencils. 

  • Graphite is used to make crucibles which are inert to acids and alkalies. 

  • Graphite is used in tennis rackets, fishing rods, aircrafts etc. 

  • Diamond is used in ornaments, polishing, lapping etc. 


Some important compounds of Carbon and Silicon 

Oxides of carbon are of great importance and are found in nature. Here we are discussing two main oxides of carbon in the table below –

Some Important Compounds of Carbon 

Oxides of Carbon 

Preparation 

Properties 

Uses 

Carbon Monoxide 

Chemical Formula – CO2

Carbon monoxide can be prepared by direct oxidation of carbon in limited supply of oxygen. 

2C + O2 🡪 2CO

It can also be prepared by dehydration of formic acid at 373 K temperature and in presence of conc. sulfuric acid. 

HCOOH 🡪 H2O + CO

At commercial level it is prepared by passing steam over hot coke. The reaction takes place at 473 – 1273 K. 

C + H2O 🡪 CO + H2

The mixture of CO and H2 is known as water gas or synthesis gas. 

Carbon monoxide can also be prepared by passing air over hot coke at 1273 K temperature. 

2C + O2 + 4N2 🡪 2CO + 4N2

Mixture of CO and N2 is called producer gas. 

Carbon monoxide is a colorless and odorless gas. 

It is insoluble in water. 

It is a strong reducing agent. Although, it cannot reduce alkali and alkaline earth metals. 

It is a poisonous gas. 

Due to its reducing property, it is used in the extraction of metals such as Zn, Fe etc. 

It is used in synthesis of many compounds. 

It is used in synthesis of metal carbonyls. 

Carbon Dioxide 

Chemical Formula – CO2

Carbon dioxide can be prepared by direct combustion of carbon or carbon fuels in excess supply of oxygen or air.

C + O2 🡪 CO2

CH4 + 2O2 🡪 CO2 + 2H2O  

It can also be prepared by the reaction of dilute hydrochloric acid and calcium carbonate. 

CaCO3 + 2HCl 🡪 CaCl2 + CO2 + H2

At commercial level, it is formed by heating limestone. 


It is colorless and odorless gas. 

It is slightly soluble in water. 

It reacts with water and forms carbonic acid. 

It is present in the atmosphere by 0.03% (by volume). 

In CO2, carbon atom is sp hybridized. 

It is not poisonous like carbon monoxide. 

It is a greenhouse gas. 

It is used in photosynthesis. 

Its solid form is called dry ice, which is used in decoration in weddings, cold buckets etc. 

It is used in production of urea. 

It is used in fire extinguishers. 


95% of the earth’s crust is composed of silica and silicates. Being a metalloid, it possesses some characteristics of metals and some of non – metals. That’s why it becomes of more use. Silicon forms many compounds which are of great use commercially. Here we are discussing three main compounds of silicon in the table below –


Some important Compounds of Silicon 

Compounds 

Preparation 

Properties 

Uses 

Silicones 

Silicones are groups of organosilicon polymers. 

They have –(RSiO)- as a repeating unit. 

They are prepared by the alkyl or aryl substituted silicon chlorides (RnSiCl(4-n)). 

R = alkyl or aryl group.

Methyl chloride and silicon reacts at 570 K temperature and in presence of Cu catalyst and gives mixture of many methyl substituted chlorosilane. On hydrolysis and condensation polymerization, it gives straight chain polymers – silicones. 

These are water repelling in nature. 

These are thermally stable and possess high dielectric strength. 

These are resistant to oxidations and various chemicals. 


These are used as greases, sealant, electrical insulators. 

These are used for waterproofing of fabrics and in cosmetic plants. 

Silicates 

The basic structural unit of silicates is SiO44-

In this silicon atom gets bonded with four oxygen atoms in tetrahedron fashion.  

By linking silicates units form chain, ring and sheet structures. 

The negative charge on silicates is neutralized by the metal ion. 

Two man made silicates are glass and cement which are used in building, furniture, utensils, decorative items etc.  

Zeolites 

Zeolites are composed of silicon, aluminium and oxygen. They are crystalline solids. 

They have a porous structure and can accommodate various cations. 


Zeolites are used as catalysts in the petrochemicals.  industry. 

Hydrated zeolites are used in ion exchangers in softening of hard water. 

They are also used in conversion of alcohols directly into gasoline. 


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