Shapes of Organic Molecules
Use this landing page for Cambridge International AS Level Chemistry Topic 13.3: the shapes of organic molecules, sp, sp2 and sp3 hybridisation, and the arrangement of σ and π bonds.
Choose a Shapes of Organic Molecules Page
The shape of an organic molecule around each carbon atom depends on how that carbon is hybridised. These pages cover the three hybridisation states and the σ and π bonds they produce, starting with the alkene.
Key idea: An sp3 carbon is tetrahedral (109.5°), an sp2 carbon is trigonal planar (120°) and an sp carbon is linear (180°). The unhybridised p orbitals form the π bonds of double and triple bonds.
Alkene Bonding
sp2 hybridisation, the σ and π bonds of the C=C double bond and why ethene is planar (13.3.2 to 13.3.4).
Start revisingAlkanes and sp3 Carbon
Tetrahedral carbon, free rotation about C–C σ bonds, and straight-chain, branched and cyclic molecules (13.3.1, 13.3.2).
Start revisingAlkynes and Nitriles: sp Carbon
Linear sp carbon, the two π bonds of a triple bond and the shape around C≡C and C≡N (13.3.2, 13.3.3).
Start revisingHow to Use These Pages
Start with alkene bonding, which introduces hybridisation through the most important example. The sp3 and sp pages will extend the same ideas to alkanes, alkynes and nitriles when they are released.
Exam focus: Describe and explain the shape of, and bond angles in, molecules containing sp, sp2 and sp3 hybridised atoms, describe the arrangement of σ and π bonds, and use the term planar for ethene.
Copyright notice: This revision page, including its written explanations, layout and teaching sequence, is produced for Online Learning System by Dr. Mohammed Al-Fatah. It is intended for student revision and may not be copied, redistributed or republished without permission.
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