The p-Block Elements — Chemistry STD 11 Science — Question
Gujarat BoardEnglish MediumSTD 11 ScienceChemistryThe p-Block Elements5 Marks
Question
Explain the following: Why does the element silicon, not form a graphite like structure whereas carbon does.
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Answer
In graphite, carbon is $\mathrm{sp}^2$-hybridised and each carbon is linked to three other carbon atoms by forming hexagonal rings. Each carbon is now left with one unhybridised p-orbital which undergoes sideways overlap to form three p-p double bonds. Thus, graphite has two-dimensional sheet like (layered) structure consisting of a number of benzene rings fused together. Silicon, on the other hand, does not form an analogue of carbon because of the following reason:
Due to bigger size and smaller electronegativity of Si than $\mathrm{C}_{\text {, }}$ it does not undergo $\mathrm{sp}^2$-hybridisation and hence it does not form p-p double bonds needed for graphite like structure. Instead, it prefers to undergo only $\mathrm{sp}^3$-hybridisation and hence silicon has diamond like three dimensional network.
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