Atoms share one, two or three electron pairs; more bonds mean shorter and stronger links.
Practise Bonding & Molecular Structure All Bonding & Molecular Structure topics
Atoms can share one, two or three electron pairs, giving single, double or triple bonds. Each bond contains exactly one sigma component along the internuclear axis, and multiple bonds add one or two pi components formed from sideways overlap of p orbitals. More shared pairs pull the nuclei closer together and increase bond energy, so bond length decreases and bond strength increases with bond order. The pi component also restricts rotation about the bond, which is why alkenes can show cis and trans isomerism. Single bonds allow free rotation.
Key ideas: Use bond order to compare: longer and weaker for single, shorter and stronger for triple. C-C is 154 pm, C=C is 134 pm and C-triple-C is 120 pm. Bond energies rise less than three-fold because a pi bond is weaker than a sigma bond: about 348, 614 and 839 kJ/mol. Count sigma bonds as one per bond and add pi bonds for each extra pair.
Common mistakes and connections: Learners think a double bond is twice as strong as a single bond, whereas it is only about 1.75 times. Another error is thinking a double bond is two identical sigma bonds. Links to sigma and pi bonding, hybridization, IR stretching frequencies and the rigidity of alkenes.
More shared pairs pull the nuclei closer: carbon-carbon bond length falls from 154 pm for a single bond to 120 pm for a triple bond. The interactive lesson shows this as a live animation or chart.
The C-C single bond in ethane is 154 pm and 348 kJ/mol, while the C-C triple bond in ethyne is 120 pm and about 839 kJ/mol.
Atoms share one, two or three electron pairs; more bonds mean shorter and stronger links.
Single Double and Triple Bonds is a beginner topic in Bonding & Molecular Structure. It needs no earlier chemistry lessons and is a good starting point.
Study these earlier topics in Bonding & Molecular Structure first: Metallic Bond, Lewis Dot Symbols, Lewis Structures.
The next topics in Bonding & Molecular Structure are Lone Pairs and Formal Charge.
Yes. The interactive lesson includes a self-check question on Single Double and Triple Bonds, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Single Double and Triple Bonds is topic 9 of 104 in Bonding & Molecular Structure.