A LITTLE LIGHTBULB MOMENT
Bonding, functional groups and nomenclature
Sigma bonds form the skeleton; pi bonds sit beside it
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Think trunk first, then side-by-side overlap for extra bonds.
The idea behind the cue
A sigma bond comes from head-on orbital overlap and is the first bond between two atoms. Pi bonds come from side-on overlap and add to sigma bonds in double and triple bonds. Single bonds are sigma only; double bonds are one sigma plus one pi; triple bonds are one sigma plus two pi.
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Short & simple
Think trunk first, then side-by-side overlap for extra bonds.
Acronym
SPDT — Sparkly Pancakes Decorate Teapots.
Story
A Lego bridge gets one thick beam down the middle, then two skateboard ramps tucked alongside it. The middle beam is the sigma bond; the ramps are pi bonds layered next to it.
Connect the pieces
- S (Sparkly) → Sigma bond: Head-on orbital overlap; this is the first bond between two atoms and the backbone of ordinary single, double, and triple bonds.
- P (Pancakes) → Pi bond: Side-on orbital overlap; pi bonds add beside a sigma bond in double and triple bonds.
- D (Decorate) → Double bond: One sigma bond plus one pi bond.
- T (Teapots) → Triple bond: One sigma bond plus two pi bonds.
- Sparkly · Sigma bond: Head-on orbital overlap; this is the first bond between two atoms and the backbone of ordinary single, double, and triple bonds.
- Pancakes · Pi bond: Side-on orbital overlap; pi bonds add beside a sigma bond in double and triple bonds.
- Decorate · Double bond: One sigma bond plus one pi bond.
- Teapots · Triple bond: One sigma bond plus two pi bonds.
Know the limits
This card describes ordinary covalent bonds in main-group organic molecules; metal bonding and aromatic delocalization are separate topics.
Further reading · OpenStax Organic Chemistry ↗Check your understanding
Which statement best describes a carbon-carbon triple bond?
A. One sigma bond and two pi bonds
B. Two sigma bonds and one pi bond
C. Three sigma bonds
D. One pi bond and two sigma bonds
Reveal explanation
One sigma bond and two pi bonds
A triple bond always contains one sigma bond formed first by head-on overlap, plus two pi bonds from side-on overlap.