Carbon and Its Compounds

Introduction

Carbon is the 15th most abundant element in earth's crust and fourth most abundant element in universe by mass after hydrogen, helium and oxygen. Carbon constitutes of only 0.2% of earth's crust and only 0.03% of carbon compound in the form of carbon dioxide present in atmosphere.

Inspite of this small amount of carbon available in nature, carbon plays very important role in our life.

Carbon is the common element found in all known form of life. Structure of all living organism contains carbon. Carbon present in living organism even after death. Coal, petroleum and its products are compounds of carbon. Carbon is an element and a non-metal.

Symbol of Carbon = C

Atomic number of carbon = 6

Atomic structure of carbon = 2, 4

Valence electrons of carbon = 4

Nature of carbon = Non-metal

Since, valency of carbon is equal to four, thus carbon is called tetravalent.

Four valency of carbon means, carbon reacts with four atoms of same or different elements to form compound.

Bonding in Carbon - The Covalent Bond

Every element forms bond in order to achieve stable configuration or electronic configuration of its nearest noble gas.

Carbon has valence electrons equal to 4. Thus, carbon can achieve stable configuration by following two ways:

(a) By losing four electrons: By losing of four electrons present in outermost orbit and forming C⁺⁴ ion, carbon can achieve the electronic configuration of helium (He).

But to remove four electrons from the outermost orbit of carbon requires large amount of energy. And after removal of four electrons, there are six protons left present in its nucleus and just two electrons left in its outermost orbit. This makes the nucleus of carbon unstable because it will become difficult to hold six protons in nucleus by just two electrons in outermost orbit.

Thus, to lose four electrons by carbon to achieve stable configuration is not possible.

(b) By gain of four electrons: If carbon gains four electron forming C^4– to form stable configuration, the number of electrons present in outermost orbit will become ten and number of protons in nucleus remains same, i.e. equal to 6. Thus, it will become difficult for only six protons in the nucleus of carbon to keep hold ten electrons in the orbits of carbon. This will also make the carbon unstable.

Thus, to gain four electrons by carbon to achieve stable configuration is also not possible.

Thus, carbon achieve stable configuration by sharing of electrons with atom of same or other elements and forms bond. Apart from carbon many other elements form bonds by sharing of electrons. Such bonds are called covalent bonds.

Covalent Bond:

Bond forms by the sharing of electrons between same or different atoms of element, is called COVALENT BOND.

Formation of single, double and triple bond

When one electron by each of the two atoms is shared, a single bond is formed. A single bond is represented by a horizontal dash (–) line.

When two electrons by each of the two atoms are shared, a double bond is formed. A double bond is represented by simply two parallel horizontal dashed (=) lines.

When three electrons by each of the two atoms are shared, a triple bond is formed. A triple bond is represented by three parallel horizontal dashed (≡) lines.

Formation of Molecules by Sharing of Electrons

Formation of Hydrogen (H₂) Molecule

Atomic Number of Hydrogen = 1

Electronic Configuration of Hydrogen = 1

Valence electrons of Hydrogen = 1

Hydrogen has one electrons present in outermost orbit. Thus, in order to achieve stable configuration, hydrogen forms bond with atom of same element or different element.

To form bond, hydrogen shares its one electron with other atom.

In the formation of hydrogen molecules, two hydrogen atoms are required. In this each of the hydrogen atoms share its one electron.

Both the atoms of hydrogen have same authority on shared electrons.

Since, hydrogen molecule (H₂) is formed because of the sharing of electrons. Thus, bond formation is this is called covalent bond and compound so formed is covalent compound.

Formation of Chlorine (Cl₂) molecule:

Atomic number of chlorine (Cl) = 17

Electronic configuration of chlorine (Cl) = 2, 8, 7

Valence electrons of chlorine (Cl) = 7

Since, a chlorine atom requires one electron to complete its octet, i.e. to achieve stable configuration, thus each of the two chlorine atoms contribute one electron, i.e. share one electron to form chlorine (Cl₂) molecule.

Since, in the formation of chlorine (Cl₂) molecule, one electron from each of the two atoms is shared, thus a single bond is formed between chlorine atoms.

Since, chlorine molecule (Cl₂) is formed because of the sharing of electrons. Thus, bond formation is this is called covalent bond and compound so formed is covalent compound.

Formation of Oxygen (O₂) molecule

Atomic number of oxygen (O) = 8

Electronic configuration of oxygen (O) = 2, 6

Valence electrons of oxygen (O) = 6

Oxygen has six electrons in its outermost orbit, thus to obtain stable electronic configuration, i.e. to complete its octet, it requires two more electrons.

Thus, each of the two atoms of oxygen contributes two electrons to share. By sharing of two electrons by each of the two oxygen atoms, each of the oxygen atoms gets eight (8) electrons in its outer most orbits.

Since, in the formation of oxygen molecule, two electrons are shared by each of the two atoms of oxygen. Thus, a double bond is formed.

Since, oxygen molecule (O₂) is formed because of the sharing of electrons. Thus, bond formation is this is called covalent bond and compound so formed is covalent compound.

Formation of Nitrogen (N₂) molecule

Atomic number of nitrogen (N) = 7

Electronic configuration of nitrogen (N) = 2, 5

Valence electron of nitrogen (N) = 5

Nitrogen has five in its outermost orbit, this means nitrogen requires three electrons to achieve stable configuration.

In the formation of nitrogen molecule (N₂), each of the two nitrogen (N) atom share three electrons, so that their outermost orbit would have eight electrons. By this nitrogen achieves stable configuration and nitrogen molecule is formed.

Since, molecule of nitrogen is formed by sharing of three electrons by each of the two atoms, thus a triple bond is formed in the molecule of nitrogen.

Since, bond is formed in nitrogen by sharing of electrons, thus bond is called covalent bond and nitrogen is called a covalent compound.

Formation of molecule of water (H₂O)

Atomic number of oxygen (O) = 8

Electronic configuration of oxygen (O) = 2, 6

Valence electrons of oxygen (O) = 6

Atomic number of hydrogen (H) = 1

Electronic configuration of hydrogen (H) = 1

Valence electron of hydrogen (H) = 1

Oxygen atom has six electrons in its outermost orbit so it requires two electrons to complete its octet i.e. to achieve stable electronic configuration. On the other hand hydrogen has one electron in its outermost orbit, so hydrogen requires one more electron to achieve stable configuration.

Thus, in the formation of water molecule, oxygen shares two electrons, i.e. one electron with each of the hydrogen atoms.

Since, molecule of water is formed because of sharing of electrons, thus bonds present in this are covalent bonds and compound is covalent compound.

Formation of carbon dioxide (CO₂)

Atomic number of carbon (C) = 6

Electronic configuration of carbon (C) = 2, 4

Valence electrons of carbon (C) = 4

Atomic number of oxygen (O) = 8

Electronic configuration of oxygen (O) = 2, 6

Valence electrons of oxygen (O) = 6

In the formation of molecule of carbon dioxide, carbon shares two electrons with each of the two oxygen atoms while each of the two oxygen atoms share two electrons with carbon atom in order to achieve stable configuration.

Bonds present in carbon dioxide are covalent bonds and carbon dioxide is called covalent compound.

Formation of Ammonia (NH₃)

Atomic number of hydrogen (H) = 1

Electronic configuration of hydrogen (H) = 1

Valence electron of hydrogen (H) = 1

Atomic number of nitrogen (N) = 7

Electronic configuration of nitrogen (N) = 2, 5

Valence electron of nitrogen (N) = 5

Atom of nitrogen requires three electrons and hydrogen atom requires one electron to achieve stable electronic configuration. Therefore, in the formation of ammonia molecule (NH₃) nitrogen atom shares three electrons with each of the three hydrogen atoms.

Since, nitrogen shares one electron with each of the three hydrogen atoms, so three single bonds are formed in the formation of ammonia molecule.

Ammonia is formed because of the sharing of electrons, thus bonds present in ammonia molecule are covalent bonds and ammonia so formed is called covalent compound.

Formation of methane (CH₄)

Atomic number of carbon (C) = 6

Electronic configuration of carbon (C) = 2, 4

Valence electrons of carbon (C) = 4

Atomic number of hydrogen (H) = 1

Electronic configuration of hydrogen (H) = 1

Valence electron of hydrogen (H) = 1

Atom of carbon has four (4) electrons in its outermost orbit so it requires four more electrons to complete its octet, i.e. to achieve stable configuration. On the other hand hydrogen has one electron in its outermost orbit, so hydrogen requires one more electron to achieve stable configuration. Hydrogen forms duet, i.e. gets two electrons in its outermost orbit to achieve the electronic configuration of helium (a noble gas), which is nearest to it.

Thus, in the formation of molecule of methane, carbon atom shares one electron with each of the four hydrogen atom and achieve stable configuration.

Since, carbon shares its four electrons, one with each of the hydrogen atom, thus four single covalent bonds are formed in the formation of molecule of methane. Since, methane is formed because of sharing of electrons, thus methane is a covalent compound.

Formation of ethane (C₂H₆)

Atomic number of carbon (C) = 6

Electronic configuration of carbon (C) = 2, 4

Valence electrons of carbon (C) = 4

Atomic number of hydrogen (H) = 1

Electronic configuration of hydrogen (H) = 1

Valence electron of hydrogen (H) = 1

In the formation of ethane (C₂H₆) each of the two carbon atoms share its three electrons with each of the three hydrogen atoms and each of the carbon atom share one electron among them.

In the formation of ethane seven single covalent bonds are formed.

Formation of ethylene (C₂H₄)

Atomic number of carbon (C) = 6

Electronic configuration of carbon (C) = 2, 4

Valence electrons of carbon (C) = 4

Atomic number of hydrogen (H) = 1

Electronic configuration of hydrogen (H) = 1

Valence electron of hydrogen (H) = 1

In the formation of ethylene (C₂H₄), two carbon atoms share two electrons among them and simultaneously these each of the two carbon atoms share two electrons with two of the hydrogen atoms.

Since, one carbon atom shares two electrons with other carbon atom, thus a double bond is formed between carbon atoms. On the other hand, each of the two carbon atoms shares one electron with two hydrogen atoms resulting formation of single bonds with all of the hydrogen atoms.

Since, ethylene is formed because of sharing of electrons, thus bonds formed in this are covalent bonds and compound is covalent compound.