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Class 10 Class 12

Carbon and its Compounds

Explain the formation of covalent bonds in (i) chlorine molecule; (ii) carbon tetrachloride and (iii) ammonia.

(i) Formation of chlorine molecule: Two chlorine atoms share one electron of each and acquire stable electronic configuration as shown:

(ii) Formation of carbon tetrachloride: Carbon atoms has four electrons in the outermost shell. In the formation of carbon tetrachloride, it shares four electrons with four chlorine atoms. In turn four chlorine atoms share one electron each with one carbon atom. Thus in all, one carbon atom and four chlorine atoms complete their octet by mutual sharing of electrons and carbon tetrachloride containing four covalent bonds is formed as shown:

(i) Formation of chlorine molecule: Two chlorine atoms share one elec

(iii) Formation of ammonia molecule: Nitrogen (N) atom has 5 electrons (2, 5) in the outermost shell. It shares one electron each of three hydrogen atoms to form ammonia molecule as shown:

(i) Formation of chlorine molecule: Two chlorine atoms share one elec

One unshared pair of electrons in ammonia molecule is not involved in bond formation and is called a lone pair of electrons.

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Discuss the reactivity of carbon in relation to its electronic configuration.

The electronic configuration of carbon is K (2), L (4). Thus it has 4 electrons in its outermost shell. In order to react or to achieve noble gas configuration, it should either gain or lose 4 electrons.
(i) It cannot gain 4 electrons and become C^4– anion because its nucleus with 6 protons cannot hold on 10 electrons.
(ii) Also it cannot lose 4 electrons and become C⁴⁺ because a very large amount of energy would be required to remove four electrons from a small atom like carbon having a very close nucleus with 6 protons.
Carbon overcomes above problem and forms a large number of compounds by sharing its valence electrons with other atoms of carbon or with atoms of other elements, thereby satisfying requirement to attain noble configuration of all the combining atoms. For example, carbon forms methane as shown below:

The electronic configuration of carbon is K (2), L (4). Thus it has 4

In methane, carbon shares its four valence electrons with four valence electrons, one each from four hydrogen atoms. Thus carbon attains the configuration 2, 8 as that of nearest noble gas, neon. And all four hydrogen atoms individually atttain the configuration of helium gas. Bond so formed due to sharing of electrons is called covalent bond.