CARBON Group
Dr Sonika Batra
CARBON
Carbon belongs to the group IV of
the periodic table.
It has four electrons in its
outermost orbit, so its valency is
four.
Group 14: The Carbon Family
Elements
▪Electron configuration is ns2np2 (n is the period
number)
▪The half filled orbital allows this group to
straddle the line between metal and non metal
▪The elements show increasing metallic character
as you go down a group
▪The heavier elements of the group are more
Group 14: The Carbon Family
▪Central element to life and natural intelligences ▪Carbon has nonmetallic properties
▪Forms Covalent bonds with nonmetals and ionic bonds with metals
▪Small radius allows for the wide occurrence of C=C and C=O bonds in compounds
Compounds of Carbon are Widely
Distributed in Nature
The number of carbon compounds is
Why so many Carbon Compounds
in nature?
Because carbon is
chemically unique.
Only carbon atoms
have the ability to
combine with
Carbon- Long Chains
A long chain, in turn, provides a
What are Allotropes ?
Allotropes
are
elements
which
are
The three carbon allotropes of carbon are
Diamond, Graphite and
Buckminster-fullerenes.
Diamond- Hardest Natural Material known.
Graphite- Conducts Electricity.
Buckminster-fullerenes- Heat resistance,
Diamond
Carbons are bonded
via sp
3hybridization
to 4 other carbon
atoms forming a giant
network covalent
Properties of Diamond
High melting point
due to strong directional
covalent bonds (3550
C)
Extremely
hard
because it is difficult to break
atoms apart or move them in relation to one
another
No electrical conductivity
because electrons are
localized in specific bonds
Graphite
Carbon atoms are
bonded via sp2
hybridization.
Carbon atoms form
Graphite Structure
Carbon has 4 valence
e- to bond with. 3
are used for closest
atoms in rings. 1 is
delocalized in
p-orbitals
The presence of
p-orbitals allows for
Properties of Graphite
Different from Diamond
Conducts electricity because of delocalized
electrons
Slippery can be used as lubricant, sheets can
easily slip past each other (think of a deck of
cards)
Same as Diamond
High melting point (higher actually because of
delocalized e-, 3653
C)
Physical Properties of
Diamond and Graphite
Property Diamond Graphite
Appearance Transparent Black, Shiny
Hardness Very Hard Soft, slippery to touch
Thermal
Conductivity Very poor moderate Electrical
Conductivity Poor Good conductor Density(kg/m3) 3510 2250
How Diamond and Graphite are
chemically identical?
These results of thes experiments answer this question:
On heating diamond or graphite in the air, they burn
completely to form carbon dioxide.
Equal quantities of diamond and graphite when burned,
Buckminster-fullerenes.
In 1985, Harold Kroto, James R. Heath, Robert
Curl and Richard Smalley discovered C60, and
fullerenes.
Its structure is special is special because it is in
Fullerenes
Buckyballs: spherical
Nanotubes: tube
shaped
Both have very
interesting properties
Super strong
Conduct electricity and heat with low
resistance
Buckyballs
Carbon atoms bond in
units of 60 atoms (C-60) forming a structure
similar to a soccerball
with interlocking six sided and five sided rings.
sp2 hybridization
Extra p-orbitals form pi
bonds resulting in
Electrical conductivity
Stronger covalent bonds,
Applications of fullerenes
•
Researchers have found that water-soluble derivates offullerenes inhibit the HIV-1 protease (enzyme responsible for the development of the virus) and are therefore useful in
fighting the HIV virus that leads to AIDS.
•
As super conductors•
Elements can be bonded with C60 or other fullerenes to create more diverse materials, including superconductors andinsulators.
The few of the applications of fullerenes
are-A.
Biological applications
B.
In cosmetics.
•
Drug Delivery
Vehicles
•
In vitro inhibition
of HIV protease
•
As anti oxidants in
cosmetics
Fullerenes form an interesting system for
Drug Delivery.
They are Strong Drug Adsorbents.
Water soluble Fullerene Derivatives which
Fullerenes offer lubricant coatings
Nanosphere powders are being developed to reduce
friction and improve wear resistance in parts where there are rolling and sliding contacts, such as:
Ball bearings
Chains
Gears
Pumps
Screws
FULLERENE IN PERSONAL CARE
PRODUCTS
It is a powerful antioxidant, reacting readily and at a
high rate with free radicals, which are often the cause of cell damage or death.
It behaves like a "radical sponge," as it can sponge-up
and neutralize 20 or more free radicals per fullerene molecule.
It possess a novel ability of selectively entering
• It enhances skin absorbtion and helps fight the appearance of fine lines, wrinkles sagging skin and dark spots caused by the oxidation of cells.
Fullerenes act as ‘radical sponges’
scavenging around 20 free radicals per molecule of fullerene.
This action is due to the electron deficient
alkene nature of fullerenes which take up the electrons and scavenge the radicals.
The efficiency of these entities goes up to
around 100 times the leading antioxidants.
Oxidation causes cell death & damage and
also deterioration of plastics, food spoilage and metal corrosion and so the application of fullerene is based on this property .
Carbides
▪
Carbides: Form when a carbon atom bonds
with a less electronegative element (In other
words carbon acts as an anion)
▪
Carbon is the only group 14 element that will
form an anion
▪
Three types of carbides: saline carbides,
▪
The methide ions are very strong Bronsted bases
1. Saline Carbides- C4- or C
2-▪
Saline Carbides are formed when metals of group 1 and 2,
aluminum, and a few other metals form ionic bonds with
carbon
▪
The
s
-block metals form saline carbides when their oxides are
heated with carbon.
▪
C
4-carbides are called methides because they produce methane
and the corresponding hydroxide in water:
Saline Carbides
▪
The species C
22-is the acetylide ion and the
carbides are commonly called acetylides
▪
Acetylide ions are very strong Bronstead bases
▪
Acetylides react with water to produce ethyne
(C
2H
2) and the corresponding hydroxide
▪
CaC
2(calcium carbide) is the most common
2 Covalent Carbides
▪
When carbon reacts with an atom that is
only slightly less electronegative than
itself and is about the same size, a covalent
carbide is formed.
▪
The most common well know covalent
3. Interstitial Carbides
▪
Interstitial carbides are the compounds formed by the
direct
reaction of a
d
-block metal and carbon at
temperature above 2000ºC
▪
In these compounds the C atoms occupy the gaps
between the metal atoms pinning the metal atoms
together into a rigid structure
▪
The materials are very hard and often have melting
Graphite intercalation compound
Graphite intercalation compounds (GICs)
are complex materials having a formula
CX
mwhere the ion X
n+or X
n−is inserted
(intercalated) between the carbon layers.
Typically m is much less than 1.
These materials are deeply colored solids
intercalation: injection of intercalant
particles between crystal layers
intercalant: particles of a different chemical
species which enter the layers
intercalation requires: strong intraplanar &
weak interplanar binding forces
Preparation and structure
These materials are prepared by treating graphite with a strong
oxidant or a strong reducing agent:
C + m X → CXm (The reaction is reversible)
The host (graphite) and the guest X interact by charge transfer.
In a graphite intercalation compound not every layer is necessarily occupied by guests.
In so-called stage 1 compounds, graphite layers and intercalated
layers alternate
in stage 2 compounds, two graphite layers with no guest
material in between alternate with an intercalated layer.
Similarly stage 3 and stage 4 have three and four layers with no
The actual composition may vary and therefore these
compounds are an example of non -stoichiometric compounds.
The layers are pushed apart upon incorporation of the guest
Classification of Intercalation Compounds
1.
Covalent graphite intercalation Compounds or non conducting intercalates These are characterised by only two substances: Graphite fluoride
and Graphite oxide
Graphite fluoride is obtained by heating the crystalline graphite with
flourine at about 700 C and then cooling down to 400-600 C, resulting in covalent linkage of C and F to give a composition of (CF)n. These compounds are chemically inert towards water, acids and bases.
Graphite oxide is obtained by the oxidation of graphite with strong
oxidizing agents (fuming nitric acid, conc sulfuric acid) Its
2. Electrovalent Intercalation Compounds or
Conducting intercalates
In these types of intercalate, graphite layers accept electrons from
intercalated species.
These compounds are formed by treatment of graphite at 300 C with molten or vapor phase lithium to give LiC6 or other alkali metals
(except sodium) to give golden yellow graphite of composition C8M. When these compounds are heated further at reduced pressure, some of the metal invades the graphite layers and the rest of the metal is lost to give various intercalates with different colors.
C8M C24M C36M C48M C60M (Bronze colored Steel Blue Blue Black Black
I stage) (Iind stage) (IIIrd stage) (IVthstage) (Vth stage)
These intercalates involve the donation of electrons from alkali metals to the conduction band of the graphite resulting in an increase in
3. Electron acceptor Metal-Graphite intercalates
In these intercalates, there is removal of electron from the top of
valence p-band.
These intercalates are formed by
a) Halogens (Chlorine and Bromine)
b) HF
c) Large number of halides including CdCl2, CuBr2, FeCl3, AlCl3, ClF3 d) A number of oxides CrO3, MoO3, SO3, N2O5
e) And some sulphides FeS2. PdS, V2S3
In these compounds there is transfer of electrons from graphite to invading atoms and electrical conductivity is increased upto ten times
▪
Central element to electronic technology and artificial
intelligences.
▪
Larger atomic size than C which results in relatively few
compounds that have Si=Si and Si=O bonds.
▪
Si compounds can act as Lewis acids where as C compounds
typically cannot.
▪
Si compounds can expand its valence shell by using its
d
orbitals
thereby allowing for the accommodation of lone pair electrons of
an Lewis base.
▪
Second most abundant atom in the earth’s crust
▪
Occurs widely in rocks as silicates (compounds containing
the silicate ion, SiO
42-)
▪
Pure silicon is obtained by reduction of quartzite (a
granular form of quartz) with high purity carbon in an
electric arc furnace
▪
Further purification is necessary before silicon can be
used in the semiconductor industry
SiCl
4(l) + 2H
2(g) ---
Si(s) + 4HCl(g)
SiO
2(s) + 2C(s)
Si(s) + 2CO(g)
Structure of Silicon
Silicon contains 4 valence
electrons
It forms a lattice similar to that
of diamond - each Si atom bonded to 4 others
Silicon is fairly unreactive and
acts as an insulator at low
temperatures as it has no free electrons
With impurities added it can
conduct electricity at low temperatures
From:
Highlights of Silicon Chemistry
Silicon bonds to oxygen to form repeating –Si–Oi– units, which are found in silicates and silicones.
The silicate building unit is the orthosilicate grouping, –SiO4 –, which has a tetrahedral arrangement.
Compounds (Oxides of Silicon)
▪ Sand is usually small fragments of quartz. The golden brown color
is caused by iron oxide impurities
▪ Silica gets its strength from its covalent bonding network
structure.
SiO2(Silica)
▪ Occurs naturally in quartz,
Properties:
Hard
Rigid network solid Insoluble in water
Structure of silicon dioxide
Commonly known as
silica and seen as sand or quartz
Like diamond, SiO2 is
also a giant covalent lattice/ structure
Each Si atom is bonded
to 4 O atoms, and each O atom is bonded to 2 Si atoms
From: http://www.moe.gov.sg/edumall/tl/digital_resources/chemistry6.htm
Properties of silicon dioxide
has a high melting point - varying depending on what
the particular structure is around 1700°C.
Very strong silicon-oxygen covalent bonds have to be
broken throughout the structure before melting occurs.
is hard. This is due to the need to break the very
strong covalent bonds.
doesn't conduct electricity. There aren't any
delocalised electrons. All the electrons are held tightly between the atoms, and aren't free to move
is insoluble in water and organic solvents. There are no
▪
Silicates can be viewed as various arrangements of
tetrahedral oxoanions (an anion of an acid that
contains oxygen) of silicon in which each Si-O
bond has considerable covalent character
▪
Differences in the internal structure of these highly
Compounds (Oxides of Silicon)
ZnSiO
4(Zircon)
▪
Used as a substitute for diamonds in jewellry
Ca
2Mg
5(Si
4O
11)
2(OH)
2(Tremolite or Asbestos)
▪
Fibrous material which can withstand extreme heat
Compounds (Oxides of Silicon)
Silicones
▪
Synthetic materials that consist of long -O-Si-O-Si- chains
with the remaining silicon bonding positions occupied by
organic groups such as the methyl group (-CH
3)
▪
Silicones are used to waterproof fabric because their
Germanium and Tin
▪Germanium is recovered from the dust of industrial plants
processing zinc ores (it occurs as an impurity in zinc).
▪Germanium is mainly used in the semiconductor industry.
▪Tin is easily obtained from it ore (cassiterite (SnO2)) by reduction
with carbon.
▪ Tin is expensive and not very strong but it is resistant to
corrosion.Its main use is in tin plating and used in alloys such as bronze.
SnO2(s) + C(s) Sn(l) + CO2(g)
LEAD (Pb)
Lead is also easily obtained from it ore (galena
(PbS)) and converted to its oxide and then reduced with coke (form of carbon)
PbO(s) + C(s) Pb(s) + CO(g)
▪ Lead is durable and malleable which makes it useful in the
construction industry
▪ In addition lead is very dense which makes it ideal as
radiation shields from x rays
▪ Lead is also used as electrodes for rechargeable batteries
Compounds (Oxides of Carbon)
CO2 (Carbon dioxide)
▪Formed when organic matter burns in the a plentiful source of air
and when animals exhale
▪CO2 is always present in air but the burning of fossil fuels is
increasing the amount of CO2 in the air which is then in-turn leading to global warming
▪CO2 is an acid anhydride of carbonic acid ▪CO2(g) + H2O(l) H2CO3(aq)
▪Carbonated beverages have high partial pressures of CO2 to drive the
Compounds (Oxides of Carbon)
▪ CO is the formula anhydride to formic acid (HCOOH) ▪ CO can be produced in the laboratory by the dehydration
of formic acid with hot, concentrated sulfuric acid
▪ CO is a reducing agent and is used in the production of a
number of metals, most notably iron in blast furnaces
HCOOH(l) + H2SO4 CO(g) + H2O(l)
CO (Carbon monoxide)
▪Formed when carbon burns in
the a limited source of air
▪This happens in cigarettes and
badly tuned automobile engines
