1. The Structure of Formaldehyde
Formaldehyde has a central carbon atom double bonded to an oxygen atom and single bonded to two hydrogen atoms. Its Lewis structure looks like this:
H
|
C = O
|
H
2. Hybridization
* Carbon's Valence Electrons: Carbon has four valence electrons (2s² 2p²)
* Hybridization: To form the bonds in formaldehyde, carbon undergoes sp² hybridization. This means:
* One 2s orbital and two 2p orbitals combine to form three sp² hybrid orbitals. These hybrid orbitals are arranged in a trigonal planar geometry, with bond angles of approximately 120°.
* The remaining 2p orbital on carbon remains unhybridized.
3. Bond Formation
* Sigma Bonds:
* Two of the sp² hybrid orbitals on carbon form sigma (σ) bonds with the 1s orbitals of the two hydrogen atoms.
* One of the sp² hybrid orbitals on carbon forms a sigma (σ) bond with the 2p orbital of the oxygen atom.
* Pi Bond:
* The unhybridized 2p orbital on carbon overlaps with an unhybridized 2p orbital on oxygen to form a pi (π) bond. This pi bond is responsible for the double bond between carbon and oxygen.
4. Summary
In summary, the carbon atom in formaldehyde is sp² hybridized, resulting in:
* Three sp² hybrid orbitals: Form sigma bonds with the two hydrogen atoms and the oxygen atom.
* One unhybridized 2p orbital: Forms a pi bond with the oxygen atom.
This hybridization and bond formation give formaldehyde a planar geometry with bond angles close to 120°.
