carbon...but what makes carbon such an interesting element can be directly attributed to its two...
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Carbon
The computer screen on which you are reading this article, the clothes
that you are wearing, the food that you eat and even the cars in which
you ride all have one thing in common. What is this thing? They all
are comprised of some element of carbon. Actually, all organic things
are made up of carbon. This is why the study of carbon and its
components is so important.
More About Carbon
The origin of the name ‘carbon’ is a Latin word ‘carbo’ which means
charcoal. This may come as a surprise to you, but it is the fourth most
abundant element in the entire universe. And it is the second most
abundant element in our bodies, the first being oxygen. As a matter of
fact, all organic substances in the world contain carbon in some form
or element, which is why it is the base for the entire branch of organic
chemistry.
Carbon Atom
The atomic number of carbon is 6, which represents the number of
electrons. It is represented by the symbol C and is a non-metal. It has
6 protons, 6 neutrons and obviously 6 electrons. A carbon atom is
considered to be special and unique because it can bond with other
carbon atoms to an almost unlimited degree. It is because its atom is
very small in size and can conveniently fit in as a part of larger
molecules. Each of its atoms has four electrons in its outer shell called
valence electrons and can form for chemical bonds with other atoms
and molecules.
Physical Properties of Carbon
The physical properties of this element vary according to its
allotropes. The two major allotropes are diamond and graphite. These
two have almost opposing physical properties.
● Whereas diamond is transparent and has no colour, graphite is
opaque and black
● Diamond is the hardest substance known to man, graphite is
soft and spongy in texture
● Now diamond cannot conduct electricity at all, graphite is a
very good conductor of electricity
● Both allotropic elements are solid, non-gaseous
● Also both diamond and graphite are insoluble in water
● It does not melt when heated, it sublimes which is it turns to
gaseous form
Uses of Carbon in daily life
Now you may not even notice but carbon is used in so many daily
activities. Some of the most important uses are:
● It makes up for 18% of the human body. Sugar, glucose,
proteins etc are all made of it. The food we eat contains an
important source of energy which we call carbohydrates.
Carbohydrates are nothing but elements of carbon itself.
● Carbon in its diamond form is used in jewellery. But diamonds
are also used for industrial purposes. It is the hardest substance
known to man and so has many uses in manufacturing
processes.
● Amorphous carbon is used to make inks and paints. It is also
used in batteries.
● Graphite is used as the lead in your pencils. It is also used in
the production of steel.
● One of the most important uses is carbon dating. We can
actually use carbon to measure the age of things. Scientists use
a rare form of carbon called Carbon-14 to measure the age of
fossils, bones etc. The release of this carbon-14 is recorded to
estimate the life of the said organic substance. This is how
scientists find the age and period of dinosaur bones and fossils!
So as you can see from the facts given above carbon is an interesting
element with uncountable uses. This is why a detailed study of it is
essential in Chemistry.
Solved Example for You
Q: Two adjacent layers in graphite are bonded by comparatively
_______ forces.
a. Strong
b. Weak
c. Loose
d. None of the above
Solution: The correct answer is option “b”. Graphite is an allotrope of
carbon. Each atom is covalently bonded to the other three atoms.
These layers slid over each other easily because of the weak Van der
Walls forces between them.
Versatile nature of Carbon
Carbon in its various forms has been known since ancient times in the
form of soot, charcoal, graphite and diamonds. Its name is derived
from a Latin word “carbo” which means “charcoal”. Ancient cultures
did not realize, of course, that these substances were different forms of
the same element. Let us explore the versatile nature of carbon.
Versatile Nature of Carbon
But what makes Carbon such an interesting element can be directly
attributed to its two unique properties, i.e. tetra-valency and
catenation. It is because of these properties that the element has the
capacity to form a large number of compounds. Not only is carbon the
fourth most abundant element in the universe, it has so far more than
three million compounds know to us till date.
The following is a deeper understanding of how these unique
properties of tetra-valency and catenation result in a highly versatile
nature of carbon:
Tetra-valency of Carbon
(Source: Wikipedia) Versatile Nature of Carbon
Carbon has the atomic number of 6, meaning each carbon atom has a
total of six electrons. Two are in the completed inner orbit, while four
electrons are found in the atom’s outermost orbit. This basically
means that carbon has four valence electrons (outer electrons that are
available for forming bonds with other atoms). Because of this
arrangement within the atom’s orbits, carbon is called tetravalent.
The carbon’s four valence electrons can be shared by other atoms (that
have electrons to share), thus forming what we call covalent bonds
(shared electrons bonds). The carbon atom also has the ability to form
a bond with other carbon atoms to create covalent bonds forming long
strings of carbon atoms, bonded to each other like links in a chain.
Silicon (Si), another element in group 14 of the periodic table, also has
four valence electrons and can make large molecules called silicones.
But due to its higher atomic number (in comparison to Carbon), its
atoms are too large to fit together into as great a variety of molecules
as carbon atoms can.
What makes carbon unique is its ability in forming covalent bonds
which are very strong in nature. The small size of the carbon atom
makes the compounds of Carbon exceptionally stable. Hence carbon
as an element has the ability to form a variety of stable compounds,
which can exist freely in nature.
Example: saturated hydrocarbons like Propane and Ethane.
Learn more about different types of Carbon Compounds here.
Catenation
The linkage of atoms of the same elements to form longer chain is
called CATENATION.
Carbon due to its tetravalent nature has the unique property to form
bonds with other atoms of carbon forming a long chain. Because of its
property of catenation, carbon can form a
● Straight chain
● Branched chain
● Cyclic ring
The astounding compound-forming ability of the element comes from
the capacity of its atoms bind to each other not only in straight chains
but in complex branchings, like the branches of a tree. They can join
in a “head-to-tail” structures to make rings of carbon atoms. The
element has practically no limit to the number or complexity of the
branches or the number of rings that can be attached to them, thus
making it unique as there is no limit to the number of different
molecules that can be formed.
Carbon atoms have the ability to share not only a single electron with
another atom forming a single bond, but it can also share two or three
electrons, forming a double or triple bond.This characteristic of carbon
allows it to form a high number of possible bond combinations at
different places, making a huge number of different possible
molecules. What is important to remember is that a molecule that
differs from even a single atom or bond position, becomes a molecule
of a different compound with different physical and chemical
properties.
Examples ● Methyl iodide (CH3-I) and Methylene iodide(CH2-l2), both
differ only in the single bond and double bond aspect, but the
properties vary distinctly and have different uses.
● Methyl iodide (CH3-I) is used as a pre-plant biocide to control
insects like a pesticide, while Methyl iodide (CH2-l2) is used as
an optical contact liquid, for determining the refractive index of
certain gemstones.
Solved Example for You
Q: A molecular formula of cyclo-hydrocarbon is similar to the
molecular formula of which of the following?
a. Alkane
b. Alkene
c. Alkyne
d. None of the above
Sol: The correct answer is option ‘b’. Cyclo-hydrocarbons have two
hydrogen atoms less than straight chain alkane. Similarly, alkenes also
have two hydrogen atoms less than alkanes.
Some Important Carbon Compounds
Carbon is a crucial element of our world. Everything that surrounds is
probably a compound of carbon. Foods, fuels, textiles, drugs
everything is either a compound of carbon or its substituent. So let us
study about some important carbon compounds.
What are Carbon Compounds?
Carbon compounds are compounds whose molecules contain a carbon
atom. They are chemical substances where a carbon atom has bonded
to an atom of another element. These compounds are generally
organic in nature. However many students are under the false
impression can if a molecule contains carbon it implies that it is
organic in nature. This is incorrect. There are various inorganic carbon
compounds as well like for example CO2 (carbon dioxide).
Now carbon compounds can be broadly divided into two categories :
Saturated Carbon Compounds
Carbon compounds that are satisfied by a single bond between them
are saturated compounds. An example of this is Ethane which is C2H6.
Here the duplet or octet of both the atoms is fully complete by only a
single bond.
Unsaturated Carbon Compound
Atoms that are satisfied only by double or triple bonds are unsaturated
carbon compounds. Ethene C2H4 is an unsaturated carbon compound,
it has a double bond.
Types of Carbon Compounds
Now let us take a look at the various types of Compounds
Organic Compounds
This is the biggest class of carbon compounds. An organic compound
must contain carbon and hydrogen. The four major categories of
organic compounds that are present in all living things are
carbohydrates, lipids, proteins and nucleic acid.
Inorganic Carbon Compounds
It is not necessary that the presence of a carbon means the compound
has to be classified as organic. Inorganic carbon compounds are rarer
than organic compounds, but they do occur. They are mostly found in
minerals and other natural sources, Some examples of inorganic
compounds are carbon disulfide (CS2), Hydrogen Cyanide (HCN) and
the most obvious one’s carbon dioxide and carbon monoxide. A few
of these inorganic carbon compounds are
● Carbites: Binary compounds formed with the atoms of carbon
and another element with an electronegativity lower than
carbon. An example would be Titanium Carbide.
● Carbonates: A carbonate is a salt of a carbonic acid. The most
common one is Calcium Carbonate CaCO3
● Cyanides: Chemical compound that contains the cyano group.
It is a carbon atom triple-bonded to a nitrogen atom. An
example would be Sodium Cyanide.
Organometallic Compounds
Compounds formed with a carbon-metal bond are known as
organometallic compounds. They are ionic compounds and are very
polar bonds due to the electropositive nature of metals.
Carbon Allotropes
Allotropes are all different physical forms of the same element. The
atoms of the element are bonded differently and this gives them
different physical and chemical properties. Like coal, graphite and
diamond are all allotropes of the carbon atom.
Carbon Alloys
Pure metals are smelted, in which coke is used as a fuel and reducing
agent. This leads to many alloys having an element of carbon in them.
The carbon steel is one such example where iron is alloyed with
carbon.
Alcohol Production: Ethanol
(Source: Wikipedia)
All alcoholic beverages in the world are actually a form of carbon
compounds. Alcoholic beverages are actually made by adding
Ethanol. The process of fermentation is used to produce ethanol
(alcohol) from glucose. One molecule of glucose gives ethanol and
carbon dioxide as by-products. So alcohols actually contain
carbohydrates.
Solved Example for You
Q: Alcoholic beverages contain which of the following?
a. Glycerol
b. Ethyl Alcohol
c. Methyl Alcohol
d. Isopropyl Alcohol
Sol: The correct answer is option “b”. Alcohol beverages contain ethyl
alcohol (ethanol), Alcohol by volume is a standard measure of how
much ethyl alcohol is contained in a given volume of an alcoholic
beverage.
Chemical properties of Carbon Compounds
Carbon is a fascinating element. It is known to form almost ten million
different compounds most of which are chemical compounds that are
organic in nature. Let us learn a bit about the chemical properties of
carbon compounds.
All carbon compounds show some common characteristic properties.
Let us see the chemical properties of carbon compounds. Four
important chemical reactions are discussed below:
Combustion Reactions:
When Carbon and its compounds burn in the presence of Oxygen (or
air), they give CO2, heat and light.The process of burning carbon and
its compounds in excess of oxygen for the release of heat and light
(energy) is known as combustion.
Following are some of the examples of the combustion reaction of
organic compounds:
C + O2 ⇨ CO2 + Heat + Light
C3H8 + 5O2 = 3CO2 + 4H2O.+ Heat + Light
(C3H8 is the molecular formula for Propane, a common gas present in
LPG which we burn for cooking in our kitchens).
In General, saturated hydrocarbons burn with a clear blue flame,
whereas unsaturated hydrocarbons burn with a yellow flame
producing soot (carbon).
Combustion of hydrocarbons may be of two types: Complete
combustion and incomplete combustion.
Complete combustion of hydrocarbons occurs in excess of
oxygen(air), producing CO2 and H2O as the only final chemical
products.Heat and light (clear blue flame) as a form of energy is
generated.
Incomplete combustion occurs when there is insufficient Oxygen(air)
and the hydrocarbon is in excess.This reaction burns with a sooty or
smokey flame and produces products which are CO(g) and/or C(s) and
H2O.
Oxidation Reactions:
In a combustion reaction, carbon compounds are oxidized in the
presence of oxygen. Though combustion is generally an oxidation
reaction, not all oxidation reactions are combustion reactions.
Oxidation is also carried out by using oxidizing agents (Oxidants).
Oxidizing agents, also referred as Oxidants are substances that oxidize
other substances while undergoing reduction themselves.
Alcohols undergo oxidation in presence of Oxidants like alkaline
potassium permanganate (KMnO4) to form carbolic acids.
Example: Ethanol undergoes oxidation to produce Acetic acid when
heated by an Oxidizing agent like alkaline KMnO4.
Addition reactions:
Unsaturated organic compounds, like alkenes and alkynes, contain
multiple bonds (C=C, C≡C) between their carbon atoms.They undergo
addition reactions to become saturated in nature.
The formation of larger molecules by addition of more radicals is
known as addition reaction.During an addition reaction of unsaturated
organic compounds, a reagent takes place at the double bonded or a
triply bonded carbon atoms.
For example; ethene is converted into ethane when heated with the
catalyst nickel.
CH2=CH2 + H2 + (Nickel catalyst) ⇨ CH3−CH3
Nickel acts as a catalyst, which basically regulates (increase/decrease)
the rate of a given reaction, without itself undergoing any chemical
change.
When ethene undergoes an addition reaction with chlorine, it gives
dichloroethane.
Chlorine is a halogen, whose atoms partially break the carbon-carbon
double bond in the alkene to a single bond and add itself across it.
Substitution Reaction:
A Substitution reaction is one in which an atom or a group of
atoms(functional group) in the compound are replaced by another
atom (or group of atoms). Substitution reactions are single
displacement reactions.
Alkanes, which have only single bonds between their carbon atoms,
are saturated hydrocarbons.They are chemically least reactive.They
are also called paraffin, as they have no affinity (minimum
affinity)towards chemical changes (parum=little;
affins=affinity).However, under suitable conditions, they undergo
substitution reactions.
For example, under the presence of Sunlight, Methane reacts with
chlorine gas to produce chloromethane and hydrogen chloride.
CH4 + Cl2 + Sunlight ⇨ CH3Cl + HCl
Sunlight (UV Light) breaks down the chlorine into free radicles,
which initiates the substitution reaction.
These reactions define the chemical properties of carbon compounds.
Solved Examples for You
Q: Addition to an alkyne is a,
a. three stage process
b. two stage process
c. single stage process
d. none of the above
Solution: The correct answer is option “b”. Addition to an alkyne is a
two-stage process alkyne ⇒ alkene ⇒ alkane
Covalent Bond
Covalent bond is a chemical bonding process in which pairs of
electrons are shared between two atoms. The force of attraction or
repulsion between two atoms, when they share electron pair or
bonding pairs, is called as Covalent Bonding. Carbon, having four
electrons in its outer shell has given it the ability to form innumerable
molecules and bonds. This is why carbon has so many elements and
allotropes. Confused as to why? It is because a carbon atom is in the
most favorable situation to form a covalent bond. Let us learn further.
What is a Covalent Bond?
Covalent bonding occurs between non-metal elements when pairs of
electrons are shared by atoms. Atoms will covalently bond with other
atoms to attain the nearest noble gas configuration. Here when
elements share their electrons, they do not become positive or
negative, since they are neither gaining or sacrificing compounds.
Thus no ions are formed by covalent bonding.
Let us learn about covalent bonding through examples given below
Covalent Bonding of Hydrogen Molecule
The simplest way to learn about covalent bond is the example of a
hydrogen molecule. Are you aware that hydrogen that is present in our
atmosphere cannot exist in its original form? It has to bond with
another atom, for it to be stable enough. This is why the molecular
formula of hydrogen is always H2.
A single atom of Hydrogen has one electron, i.e. its atomic number 1.
It has its only electron in its first and only orbit. Now to be a stable
molecule it needs to complete its duplet state. So a single hydrogen
atom will remain unstable unit it attains one more electron. So we can
say the valency of hydrogen is 1. The valency of an atom depends on
its sharing capacity. So the hydrogen atom shares its single atom with
another hydrogen atom. Now both hydrogen atoms have two (shared)
electrons in its outer shell and it is a stable molecule H2. This bond
formed by sharing electrons is nothing but a covalent bond.
Covalent Bonding of Carbon Compounds
Covalent carbon compounds are those where there is a carbon-carbon
bond. These covalent compounds have stronger bonds than other
compounds. This is because carbon is a small atom. Its nucleus has a
strong force of attraction and holds these bonds tightly together. So
covalent carbon compounds have a strong bond between themselves.
Now let us understand why the covalent bonding is so relevant for
carbon atoms.
As you are aware the reactivity of elements is its ability to lose or gain
electrons from so that its outermost shell has a complete octet (or
duplet in case of hydrogen) namely attain noble gas configuration.
However, carbon has a unique situation. It has four electrons in its
outermost shell, so one of the following situations must happen.
Situations ● It can loose the four electrons in its last shell and become a
cation i.e. C4+. However to lose all four of these electrons
would require a large amount of energy, and the resulting atom
would be unstable with six neutrons holding only two electrons
in one shell.
● The other option a carbon atom has is to obviously gain four
electrons from another atom. But it would be extremely
difficult for the resulting carbon atom to be stable. Ten
electrons will have to be held by six neutrons in the nucleus.
So instead, carbon comes up with a unique solution. It shares its
valence electrons with those of other carbon atoms, or even atoms of
other elements. Now these shared atoms of the last shell, belong to
both the atoms, hence forming a bond between these atoms. Now both
atoms have a complete outer shell with eight atoms and have both
attained noble gas configuration. This sharing of atoms, instead of
gaining or losing is called covalent bonding. And Carbon, since its
atomic number is 6, and it has four electrons in the last shell has the
most favourable structure for covalent bonding.
Some Important Carbon Compounds with Covalent Bonds
Methane: Now let us take a look at covalent bonding in some carbon
elements. Let’s get started with that of Methane. Its chemical formula
is CH4. Now that means one atom of carbon combines with four atoms
of Hydrogen to make one molecule of methane. All the hydrogen
atoms have only one electron in their outermost shell and carbon has
four. So carbon shares each of its four electrons with one atom of
carbon. This way carbon now has a complete octet and all four
hydrogen atoms have a complete duplet.
Carbon dioxide: Let us take a look at another element you should be
very familiar with, carbon dioxide. Here two atoms of oxygen
combine with one atom of carbon thus giving us the molecule CO2. As
we already know now that carbon has four electrons in its outer shell,
whereas oxygen with atomic number 8, has six atoms in the last shell.
So carbon shares two of its atoms with each atom of oxygen. This way
all three atoms complete their octet giving us one stable molecule.
Solved Example for You
Q: Which one of the following contains ionic, covalent and coordinate
bonds?
a. NaOH
b. NaCl
c. NaCN
d. NaNC
Sol: The correct answer is option ‘d’. NaNC contains ionic, covalent
and coordinate bonds. An ionic bond is present in Na+ ion and –NC
ion. A covalent bond is present between C and N atoms. Coordinate
bond is also present between C and N atoms.