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The hybridization state and shape of a carbocation is:

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Correct Answer: B. sp2 and trigonal planar
On the surface: A carbocation is bonded to 3 substituents (i.e. ORG 4.2.1) and so it is in the middle of a flat triangle: trigonal planar.
When carbon has:
4 subtituents: sp3 and tetrahedral (109.5º)
3 subtituents: sp2 and trigonal planar (120º)
2 subtituents: sp and linear (180º)
Going Deeper: There are three bonding electron pairs around the carbon atom, and these can be placed as far apart as possible in an sp2 trigonal planar framework. The empty orbital, which results in the charge, is the 2pz atomic (unhybridized) orbital (ORG 1.2, 1.3; CHM 3.5).
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