(a) Why does carbon form compounds mainly by covalent bonding?
(b) Why do covalent compounds have low melting and boiling points?
(c) Give the electron dot structure of:
(i) N2 (ii) C2H6
(d) Name the following compound.
(a) Why covalent compounds are generally poor conductors of electricity?
(b) Name the gas evolved when ethanoic acid is added to sodium carbonate. How would you prove the presence of this gas?
(c) Write the structural formula of two isomers of n- pentane C5H12.
(a) Carbon has 4 electrons in its valence shell. To attain stability, it should either gain 4 electrons or lose 4 electrons. It cannot lose 4 electrons as it involves a lot of energy. Also, it cannot gain 4 electrons because the nucleus cannot hold on to the four extra electrons added. Therefore, to complete the octet, it shares 4 electrons with other atoms. That is why, carbon forms compounds mainly by covalent bonding.
(b) Covalent compounds have covalent bonding in them. The bonds are formed by sharing of electrons. There are no ions in such compounds. There are weak forces of attraction between the molecules. So, they have low melting and boiling points.
(c) (i) N2
(a) Covalent compounds involve covalent bonding. There are no ions in the covalent compounds. Hence they are poor conductors of electricity.
(b) Carbon dioxide gas is evolved.
It turns lime water milky.
(c) Structural isomers of pentane
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