Question

Carbon and silicon both belong to the group 14, but inspite of the stoichiometric similarity, the dioxides, (i.e., carbon dioxide and silicon dioxide), differ in their structures. Comment.

Answer 1

Carbon, the first member of group 14 possesses a pronounced ability to form stable p-p multiple bonds with itself and with other first row elements such as nitrogen and oxygen. In CO₂, both the oxygen atoms are linked with carbon atom by double bonds.

\[\ce{O \overset{σ}{\underset{π}{=}} C \overset{σ}{\underset{π}{=}} O}\]

However, silicon shows its reluctance in forming p-p multiple bonding due to large atomic size. Thus, in Si0₂, oxygen atoms are linked to silicon atom by single covalent bonds giving three-dimensional network.

\[\begin{array}{cc}
\phantom{.}|\phantom{.........}|\phantom{..}\\
\phantom{.}\ce{O}\phantom{........}\ce{O}\phantom{..}\\
\phantom{.}|\phantom{.........}|\phantom{..}\\
\ce{- O - Si - O - Si - O -}\\
\phantom{.}|\phantom{.........}|\phantom{..}\\\
\phantom{.}\ce{O}\phantom{........}\ce{O}\phantom{..}\\
\phantom{.}|\phantom{.........}|\phantom{..}
\end{array}\]