define hybridization. explain the structure of C₂H₂ with orbital diagram

Dear student,

Hybridization is defined as the mixing of the atomic orbitals belonging to the same atom but having slightly different energies so that the same no. of new orbitals are formed which have equivalent energy and identical shapes. These new orbitals are called as hybrid orbitals.

Depending on the combination of atomic orbitals the hybridization may be of various types as; sp³ (1s and 3p orbitals combine to form 4 sp³ hybrid orbital.) , sp² , dsp² , sp etc.

=> sp- hybridization arises when one s and one p orbital combine to form two sp-orbital with 180° bond angle and linear shape to the molecule. The percentage of s and p are 50 %. Ex: C₂H₂ (acetylene)

=> sp² hybridization arises when one s and two p orbitals combine to form three sp² hybrid orbitals with bond angle of 120° and triangular planner shape where the s-character is 33.33% . Ex: C₂H₄ (Ethylene)

=> sp³ hybridization arises when 1s and 3p orbitals combine to form 4 sp³ hybrid orbital with bond angle 109°''28' and shape as tetrahedral where the s-character is 25% . Ex C₂H₆ (Ethane)

Ethene is represented as:

The molecule is built from H atom (1s¹) and carbon atom ( 1s² 2s² 2p¹_x  2p¹_y 2p¹_z)

In valence shell carbon has only two unpaired electrons which are not enough for formation of 4 bonds. Thus in carbon an electron is promoted from 2s orbital to empty 2p orbital to give 4 unpaired electrons.

Carbon is now in its excited state.

In ethane molecule carbon use the 2s electron and two of the 2p electrons to form new three sp² hybrid orbital .The three sp² orbitals form sigma bond with two hydrogen atoms and one carbon atom. The unhybridised 2p orbitals of both the carbon form pi bonds.

Regards