CIE A Level Chemistry: Shapes and Hybridisation of Organic Molecules

Aliphatic Compounds

Organic molecules without a benzene ring.

Straight-chain Molecules

Carbon atoms connected in one continuous chain.

Branched Molecules

Molecules with side groups attached to the main chain.

Cyclic Molecules

Carbon atoms connected in a ring structure.

Hybridisation

Mixing of atomic orbitals to form new orbitals.

sp Hybridisation

Carbon forms four σ bonds, tetrahedral shape.

Bond Angles (sp)

109.5 degrees in sp hybridised molecules.

Ethane

Example of sp hybridised molecule with tetrahedral shape.

sp² Hybridisation

Carbon forms three σ bonds, planar shape.

Bond Angles (sp²)

120 degrees in sp² hybridised molecules.

Ethene

Example of sp² hybridised molecule with planar shape.

sp³ Hybridisation

Carbon forms two σ bonds, linear shape.

Bond Angles (sp³)

180 degrees in sp³ hybridised molecules.

Ethyne

Example of sp hybridised molecule with linear shape.

Sigma Bonds (σ)

Bonds formed by end-on overlap of orbitals.

Pi Bonds (π)

Bonds formed by sideways overlap of p orbitals.

Bond Strength Order

Single < double < triple bond strength.

Planar Molecules

Molecules with all atoms in the same plane.

Trigonal Planar

Arrangement with bond angles of 120 degrees.

Linear Arrangement

Arrangement with bond angles of 180 degrees.

Ethene Planarity

Ethene has a planar configuration due to sp².

Propene Planarity

Propene has both planar and tetrahedral centers.

Ethyne Planarity

Ethyne is linear with one planar center.

Propyne Planarity

Propyne has one planar center around triple bond.

Electron Density in σ Bonds

Symmetrical about the line joining nuclei.

Overlap in π Bonds

Lobes lie above and below the atomic plane.

Double Bond

Combination of one σ bond and one π bond.

Triple Bond

Combination of one σ bond and two π bonds.