`C_(2)H_(4)`:
The electronic configuration of C-atom in the excited state is :
`""_(6)C=1s^(2)2s^(1)2p_(x)^(1)2p_(y)^(1)2p_(z)^(1)`
In the formation of an ethane molecule `(C_(2)H_(4))`, one `sp^(2)` hybrid orbital of carbobn overlaps a `sp^(2)` hybridized orbital of another carbon atom, thereby forming a C-C sigma bond. The remaining two `sp^(2)` orbitals of each carbon atom form a `sp^(2)-S` sigma bond with two hydrogen atoms. The unhybridized orbital of one carbon atom undergoes sidewise overlap with the orbital of a similar kind present on another carbon atom to form a weak `pi`-bond.
`C_(2)H_(2)`
In the formation of `C_(2)H_(2)` molecule, each c-atom is sp hybirdized with two 2p-orbitals in an unhybridized state.
One sp orbital of each carbon atom overlaps with the other along the internuclear axis forming a C-C sigma bond. The second sp orbital of each C-atom overlaps a half-filled 1s-orbital to form a `sigma` bond.
The two unhybirdized 2p-orbitals of the first carbon undergo sidewise overlap with the 2p orbital of another carbon atom, thereby forming two pi `(pi)` bonds between carbon atoms. Hence, the triple bond between two carbon atoms is mad3e up of one sigma and two `pi`-bonds.
