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Why carbon forms covalent compounds whereas lead forms ionic compounds ? |
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Answer» Solution :Carbon cannot lose all the four valence electrons to form `C^(4+)` ions because the sum of the first four ioniatization enthalpies of carbon is very large. It alsocannot GAIN four electronto form `C^(4-)`ion as their anionwould be highlyunstablebecause it would be very difficultfor a nucleuswith only 6 protons to hold on family 10 electrons. Therefore,carbon forms only covalentcompounds by SHARING of electrons: In contrast due to inert pair effect, +2 oxidationstate of PB is more stablethanits +4 oxidationstate. Further on movingdown the group, the ionization enthalpy decreases. As a result , the sum of the first two IONIZATIONENTHALPIES of Pb is quitelow and hence Pb caneasily lose two electronsto form `Pb^(2+)` ions. Consequently, Pb form ionic compounds. |
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