MediumChemistryHigh School (11–12)Chemical Bonding › Shapes of Molecules and HybridisationConceptual
Ethene, CH₂=CH₂, is flat. What is the hybridisation of each carbon atom?
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Ethene, , is flat. What is the hybridisation of each carbon atom? Which orbitals overlap to form the C-C sigma bond, the C-H bonds and the pi bond? How many sigma and pi bonds are there in all?
Need a reminder? The key ideaShow
Hybridisation mixes atomic orbitals of nearly equal energy into the same number of equal hybrid orbitals. Two pairs on the central atom give sp (180°), three give sp2 (120°), four give sp3 (109.5°), five give sp3d (trigonal bipyramidal) and six give sp3d2 (octahedral). The s-character of each hybrid is 100% divided by the number of orbitals that mix. Unhybridised p orbitals form pi bonds.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Hybridisation. Each carbon forms three sigma bonds, so it uses three hybrids: .
Step 2. C-C sigma bond. One hybrid of each carbon, head on.
Step 3. C-H bonds. The other two hybrids of each carbon overlap orbitals of hydrogen.
Step 4. Pi bond. The unhybridised orbital of each carbon stands upright to the plane. The two overlap sideways, above and below it.
Answer: both carbons are ; there are sigma bonds and pi bond.
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