Why carbon froms covalent compounds whereas lead forms ionic compounds ?

Explanation

The size of carbon atom is very small and its ionisation enthalpy is also quite high. To form `C^(4+)` ion, carbon atom has to part with all the four valence electrons. Similarly , to form `C^(4-)` ion, it has to accept four electrons. Both are not energetically favoured due to high energy involved. As a result the compounds of carbon are covalent in which carbon completes its octet as a result of electron sharing. Lead, the last member of the family has minimum ionisation enthalpy. Therefore, it is comparatively easy for the element to lose its valence electrons and to form ionic compound. the compounds involving `Pb^(2+)` ion are mostly ionic in nature.