Carbon and carbon compounds

Introduction

The word carbon is derived from Latin: carbo meaning  "coal". It is a chemical element represented by  the symbol C and has  atomic number 6. It is nonmetallic and trivalent structure as it makes available four electrons to form covalent chemical bonds. Carbon belongs to group 14 of the periodic table and it was discovered by a French scientist Antoine Lavoisier. Carbon is the hardest and highly versatile structure, usually found in materials such as diamonds and graphite. There are a variety of  forms, in which carbon is present, some of them could be our  day-to-day articles such as pencils, bags, and some electric equipment. Our atmosphere also contains some carbon in the form of C02 gas. On the other hand, earth’s crust has a minimal amount of (0.02%) carbon in the form of carbonates, hydrogen, coal and petroleum products, One of the important features of carbon is its versatility and ability to form strong bonds with many other elements.

Carbon- facts and figures

  1. Carbon has an atomic number 6,and  atomic weight 12.

  2. Its allotropes are graphite, diamond, amorphous carbon in the form of coal, graphene, etc.

  3.  Carbon has 4 electrons in its valence shell.

  4. The density of carbon is 2.2670 grams per cubic centimeter.

  5. Carbon retains its original solid-state in the room temperature

  6. Melting Point of carbon is very high .i,e  6,422 degrees Fahrenheit (ca. 3,550 degree Celsius) or 3,550   degree C.

  7. Boiling Point of carbon is  6,872 F (3,800 C) (sublimation) and it is present in about 15  isotopes  and the most common isotopes are  carbon-12 (6 protons, 6 neutrons and 6 electrons) and carbon-13 (6 protons, 7 neutrons and 6 electrons).

 

The covalent bond in the carbon

A covalent bond is a chemical bond in which, pairs of electrons are shared between the two atoms. The force at which the attraction or repulsion takes place between the two atoms while sharing their electron pair is known as covalent bonding. Carbon has 4 electrons in its outer shell and it has the ability to form the innumerable number of molecules and bonds by mutually sharing the electrons. Because of the nature of carbon sharing electrons freely, it exists in many variants (allotropes). A carbon–carbon bond is a covalent bond between 2 carbon atoms with the most common form is being  the single bond where  a bond contains 2 electrons; one from each of the two atoms. Carbon atoms can also form double bonds in compounds like  alkenes and  triple bonds in compounds called alkynes. Most of the ionic compounds have higher melting and boiling points, and they are also good conductors of electricity in their liquid form (molten state) which is attributed to their nature of bonding i,e covalent bonding. Some properties of carbon compounds are explained in the table below.

 

Melting and boiling points of common carbon compounds

 

Compound

 

 

Melting  point

 

Boiling point

Acetic acid (CH3COOH)

 

290

391

Chloroform (CHCl3)

 

209

334

Ethanol (CH3CH2OH)

 

156

351

Methane (CH4)

90

111

 

 

Some examples of covalent bonding

1. Covalent Bonding of Hydrogen Molecule

The hydrogen molecule is the simplest substance with a covalent bond between the 2 hydrogen. It is formed by the 2 atoms, each with one electron in first orbital. Both hydrogen atoms share the two electrons in the covalent bond, and each acquires a helium-like electron configuration. Hydrogen  cannot exist in its original form hence, it needs another atom to form H2. In a hydrogen molecule , there is a single atom of hydrogen with one electron hence its atomic number is 1, to put it the other way,  it has a single electron in its first and the only orbit. As already mentioned, it should be in H2 form to acquire a stable state, hence, it remains unstable until it attains one more electron to form H2. Here the valency of hydrogen is 1.  Ultimately, both the hydrogen atoms have two shared electrons in their outer shell to form a stable molecule of H2. The bond used to share the hydrogen is called a covalent bond.

 

2. Covalent Bonding of Carbon Compounds

Covalent bonds are formed from the 2 carbon molecules by forming a carbon-carbon bond. The ability to form a covalent bond in a carbon compound is because of the nature of readily gaining or losing the electrons necessary for the reactivity of elements. Consequently, carbon receives  4 electrons in its outermost shell. But, one of the following circumstances must be present in order to form a covalent bond.

  1. Carbon can lose all the 4 electrons to become a complete cation i.e. C4+. But, in order to lose all 4, it requires a lot of energy, and the final atom is highly unstable with 6 neutrons holding only two electrons in one shell which creates an imbalance.

  2. The next option is that a carbon atom can completely gain 4 electrons from another atom, but, the resulting carbon atom won’t be stable.  If it happens so, then 10 electrons must be held by six neutrons in the nucleus.

  3. Since both the above equations are impossible, carbon forms a unique bonding strategy by sharing its valence electrons with other carbon atoms or even atoms of other elements.

  4. The shared atoms of the last shell belong to both the atoms, hence forming a bond between these atoms can lead to a completely balanced outer shell with 8 atoms. At the same time, both atoms attain a noble gas configuration. 

 

Important carbon compounds with their covalent bonding

1. Methane

Methane is indicated by symbol CH4. In the methane,  a single atom of carbon combines with 4 atoms of hydrogen to configure one molecule. All 4 hydrogen atoms have a single electron in their outermost shell but a single carbon has 4 electrons. Consequently, carbon will share each of the 4 electrons with one atom of carbon and this makes carbon a complete octet with all 4 hydrogen atoms having a complete duplex. In methane, Carbon has 4 unshared electrons in its valence shell which looks imbalanced. In order to balance the octet, carbon requires 4 additional electrons and those are donated by 4 hydrogen atoms result in the formation of  4 covalent bonds from all 4 sides. The covalent bonds in this case are known as non-polar covalent bonds as the end result of such an equal sharing of electrons between carbon and hydrogen is that there is no charge separation or dipole movement in the final structure.

 

2. Carbon dioxide

If you take an  example of CO2 molecule, it is formed by combining 2 atoms of oxygen with one atom of carbon. Since carbon has 4 free-electrons in its outer shell,  and the oxygen with 6 atoms in the last shell, carbon shares 2  of the atoms with each atom of the oxygen. This phenomenon will complete their octet giving us one stable co2 molecule.

 

 

Read More

1.  

versatile nature of carbon

2.

Carbocation

3.

Carbon and its reactions

4.    

Important trends and anomalous behavior of carbon

 

Check your understanding

  1. Name any 3 allotropes of carbon

  2. Why is carbon is very tough ?

  3. Where is carbon found abundantly?

  4. Explain the nature of a covalent bond in methane.

 



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