Textbook Question
The lactic acid molecule, CH3CH(OH)COOH, gives sour milk its unpleasant, sour taste. e. What are the approximate bond angles around each carbon atom in the molecule?
12. Molecular Shapes & Valence Bond Theory
Bond Angles
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What are the H−N−H bond angles in NH3?
A
~90°
B
<109.5°
C
~109.5°
D
>120°
E
~180°
Verified step by step guidance1
First, identify the molecular geometry of NH3. Ammonia (NH3) has a central nitrogen atom bonded to three hydrogen atoms and one lone pair of electrons.
Understand that the presence of the lone pair affects the bond angles. The electron pair geometry is tetrahedral, but the molecular shape is trigonal pyramidal due to the lone pair.
Recall that in a perfect tetrahedral geometry, the bond angles are approximately 109.5°. However, the lone pair exerts a greater repulsive force than the bonded pairs, slightly reducing the bond angle.
Consider the effect of the lone pair on the bond angles. The repulsion from the lone pair pushes the hydrogen atoms closer together, resulting in bond angles less than 109.5°.
Conclude that the H-N-H bond angles in NH3 are approximately 107°, which is typical for a trigonal pyramidal shape with a lone pair on the central atom.
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