Intermediate Topic 170 of 1102 Bonding & Molecular Structure
sp2 Hybridization
One s and two p orbitals form three planar hybrids at 120 degrees, as in ethene.
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In-depth explanation of sp2 Hybridization
sp2 hybridization mixes one s orbital and two p orbitals to form three equivalent hybrid orbitals lying in a plane at 120 degrees to one another. The remaining unhybridized p orbital is perpendicular to that plane and forms a pi bond with a neighbour. Each sp2 hybrid carbon has about 33 percent s character. This hybridization describes alkenes, aromatic rings and carbonyl groups, where a trigonal planar geometry is observed. The planar arrangement makes these molecules rigid around the double bond.
Going deeper: sp2 Hybridization
Key ideas: Applies to steric number 3: carbon in alkenes, carbonyls, arenes, carbocations, and boron in BF3. The unhybridized p orbital forms the pi bond. Bond lengths: C=C 134 pm, C-C in sp2-sp2 is 147 pm (shorter than ethane 154). Conjugation in a chain requires all atoms to be sp2 so that the p orbitals align.
Common mistakes and connections: Students frequently assign sp3 to carbon in carbonyl groups, or forget that atoms like N in amides and O in esters can be sp2 due to resonance, giving planar geometry. Also carbocations are sp2 with an empty p, and carbanions are usually sp3. Links to conjugation, aromaticity, planar peptide bonds and alkene reactivity.
Visualization of sp2 Hybridization
Each carbon in ethene uses three sp2 hybrids for sigma bonds at 120 degrees in a plane, leaving one unhybridized p orbital to form the pi bond. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Each carbon atom in benzene is sp2 hybridized, with three sigma bonds in the ring plane and one p orbital above and below it.
Frequently asked questions about sp2 Hybridization
What is sp2 Hybridization?
One s and two p orbitals form three planar hybrids at 120 degrees, as in ethene.
Is sp2 Hybridization a beginner, intermediate or advanced topic?
sp2 Hybridization is a intermediate topic in Bonding & Molecular Structure. It builds on the vocabulary of beginner topics in this area.
What should I learn before sp2 Hybridization?
Study these earlier topics in Bonding & Molecular Structure first: Pi Bond, Hybridization, sp3 Hybridization.
What comes after sp2 Hybridization?
The next topics in Bonding & Molecular Structure are sp Hybridization and sp3d and sp3d2 Hybridization.
Can I practise sp2 Hybridization with quizzes?
Yes. The interactive lesson includes a self-check question on sp2 Hybridization, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Where sp2 Hybridization fits in Bonding & Molecular Structure
sp2 Hybridization is topic 55 of 104 in Bonding & Molecular Structure.