Question

Draw the molecular orbitals in the molecules of methane and acetylene. Precise the nature of the chemical bonds (pi or sigma).

Answer 1

Methane - CH₄

Carbon in sp³ hybrid state . There are 4 sp³ hybrid orbitals and form 4 ? bonds by combining with s orbital of hydrogen.

Sigma () bonds ơ sp3-5 Sigma (a) bonds sp3 hybrid orbitals

While in actylene or ethyne HC=CH both carbon atoms are in sp hybridised state . 2 sp hybridised orbitals are formed on each carbon atom. one of these sp hybrid orbital of one crbon atom combine with sp hybrid orbital of the other forming a C-C ? bond . Remaining sp orbital on each carbon atom combine with s orbital of hydrogen forming 2C-H ? bonds.There are two unhybridised p orbitals on each carbon atoms and they overlapp sideways and form 2 ? bonds (between two carbon atoms).

π bonds σ bonds σ s-sp σ bonds σ s-sp σ bonds σ sp-sp