CAIE A-Level Chemistry 13.3.2 Hybridisation, Shape and Bond Angles

Practise predicting shapes and bond angles around sp, sp2 and sp3 hybridised atoms in organic molecules.

Exam points

identify sp centres as linear with 180° bond angles and sp2 centres as trigonal planar near 120°
identify saturated carbon as sp3 and tetrahedral with bond angles close to 109.5°
apply the local geometry to each labelled atom rather than assigning one hybridisation to the whole molecule

[Maximum number: 4]

$4 \vec{P}, Q$ and R all have the molecular formula $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}$ . They are all structural isomers of each other.
P and Q each contain an oxygen atom bonded directly to a carbon atom that is $\mathrm{sp}^{2}$ hybridised. R contains an oxygen atom bonded directly to a carbon atom that is $\mathrm{sp}^{3}$ hybridised.

(a)

Explain how $\mathrm{sp}^{2}$ and $\mathrm{sp}^{3}$ hybridisation can occur in carbon atoms.
$\mathrm{sp}^{2}$ hybridisation
$\mathrm{sp}^{3}$ hybridisation

[ 2 ]

$\mathrm{sp}^{2}$ overlap of (2)s with two (2)p (atomic) orbitals

$\mathrm{sp}^{3} \quad$ overlap of (2)s with all three (2)p (atomic) orbitals

(b)

State the bond angles normally associated with each type of hybridisation in carbon atoms.
$\mathrm{sp}^{2}$ $\mathrm{sp}^{3}$

[ 2 ]

$\mathrm{sp}^{2}=116^{\circ}-124^{\circ}$ $\mathrm{sp}^{3}=106^{\circ}-112^{\circ}$

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13.3.2—Shape of, and bond angles in, molecules question 1

Question (a)

Question (b)