Q3P - Chemistry: Molecular Nature Of Matter And Change

Question

How do carbon and silicon differ with regard to the types of orbitals available forhybridization? Explain.

Step-by-Step Solution

Answer

Carbon atoms form upto 4 hybrid orbitals as its outer level has only 2s and 2porbitals available whereasSilicon has 3d orbitalsavailable for bonding in its outer level in addition to3s and 3p, to form upto 6 hybrid orbitals.

Step1: hybridization of carbon

Inthe valence electron configuration of carbon,the two unpaired 2pelectrons areused to form compounds with only two covalent bonds.After promotion 2s orbital and the three 2p orbitals of carbon are used to give a set of four degenerate ${\mathbf{sp}}^{\mathbf{3}}$ hybrid orbitalsas there are no 2d atomic orbitals.For 3d orbitals of carbon high amount of energy is needed which is not possible.

Step2:hybridization of silicon

As silicon has 3d vacant orbitals in addition to 3sand 3p orbitals for bonding.After promotion, it can form a different hybrid orbital by using its 3dorbital.The energy difference is less between 3p and 3d orbital needed for promotion.