Trigonal pyramid (chemistry)
From Biocrawler, the free encyclopedia.
In chemistry, a trigonal pyramid is a molecular geometry with one atom at the apex and three atoms at the corners of a trigonal base. One example of a molecule with a trigonal pyramidal geometry is ammonia (NH3).
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Trigonal pyramidal geometry in ammonia
The nitrogen atom in ammonia has 5 valence electrons and bonds with three hydrogen atoms to complete the octet. This would result in a tetrahedral geometry with each bond angle 109.5°. The three hydrogen atoms are repulsed by the electron lone pair in a way that the geometry is distorted to a trigonal pyramid with bond angles of 107°. Contrast to boron trifluoride with a flat trigonal planar geometry because boron does not have a lone pair of electrons.
In ammonia the trigonal pyramid undergoes rapid nitrogen inversion
