Question

Explain the bond formation in ethylene.

Answer 1

The bonding in ethylene can be explained using the hybridization concept. The molecular formula of ethylene is C₂H₄. The valency of carbon is 4. The electronic configuration of valence shell of carbon in ground state is [He] 2s² 2p_x¹ 2p_y¹ 2p_z⁰. To satisfy the valency of carbon promote an electron from 2s orbital to 2p_z orbital in the excited state.

In ethylene both the carbon atoms undergo sp² hybridization involving 2s, 2p_x, and 2p_y, orbitals, resulting in three equivalent sp² hybridised orbitals lying in the XY plane at an angle of 120° to each other. The unhybridized 2p_z orbital lies perpendicular to the XY plane.

Formation of sigma bond:

One of the sp² hybridised orbitals of each carbon lying on the molecular axis (x-axis) linearly overlaps with each other resulting in the formation of a C-C sigma bond. The other two sp² hybridised orbitals of both carbons linearly overlap with the four is orbitals of four hydrogen atoms leading to the formation of two C-H sigma bonds on each carbon.

Formation of Pi (π ) bond: