Question

Draw sigma only molecular orbital diagram for CH4 assuming square planar geometry.

Answer 1

The carbon atom central to the methane molecule has 4 valence electrons and thus needs 4 more electrons from four hydrogen atoms to complete its octet. The hydrogen atoms have a 109 degree bond angle giving the molecule a tetrahedral geometry .

Also, we can discuss as follows:

Molecular Orbital Diagram for Methane :

Sigma and pi covalent bond models have proven to be valuable tools for describing the structure and reactivity of simple molecules, such as methane and ethene. However, such models do not accurately represent the electron distribution within the molecules. In the case of methane, this model implies four eqivalent localized orbitals between the hydrogen atoms and the central carbon. However, the following orbital correlation diagram shows one lower energy occupied orbital and three degenerate higher energy occupied orbitals. All of these bonding molecular orbitals, designated φ, are delocalized and encompass several nuclei; but in each case there is a region of electron density between the carbon and more than one hydrogen. There are, of course four unoccupied antibonding orbitals having still higher energies.

Note that the carbon 1s orbital is omitted from the diagram, since it does not contribute to the bonding.