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Propene is CH₃CH=CH₂. Count its sigma bonds and its pi bonds…
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Propene is . Count its sigma bonds and its pi bonds. How many of its carbon atoms are hybridised?
Need a reminder? The key ideaShow
Carbon forms four bonds. Four atoms around it: , tetrahedral, 109.5 degrees. Three atoms around it: , planar, 120 degrees. Two atoms around it: , linear, 180 degrees. Every bond holds one sigma bond. A double bond adds one pi bond, and a triple bond adds two. In a bond-line drawing, every corner and every end is a carbon atom, and each carbon has four bonds in all.
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. The bonds. There are two C-C bonds and six C-H bonds, so eight bonds in all. One of the C-C bonds is double.
Step 2. Sigma. Each of the eight bonds holds one sigma bond, so there are 8.
Step 3. Pi. The double bond holds one pi bond in addition, so there is 1.
Step 4. Hybridisation. The carbon has four atoms around it: . The other two carbons have three each: .
Answer: 8 sigma bonds, 1 pi bond and 2 carbons.
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