A generic trigonal planar molecule showing ideal bond angle.
The general structure of a trigonal planar molecule, with the central atom labelled pink.
In chemistry, trigonal planar is a molecular
geometry with one atom at the center and three atoms at the corners of a triangle all in one plane. In a trigonal planar
molecule where all three attached atoms are identical, all bond angles will be 120° and the molecule will belong to
point group D3h. Molecules where these atoms differ − such as H2CO − as well as more complex molecules − such as alkenes − will deviate from this ideal
geometry due to lowered molecular symmetry. In general the atomic orbitals of a
trigonal planar molecule are sp2 hybridized.
Examples of molecules with a trigonal planar geometry include boron trifluoride BF3, formaldehyde H2CO,
and sulfur trioxide SO3. Some ions with trigonal planar geometry include the
nitrate ion, NO3−, the carbonate ion,
CO32−, and the borate ion, BO33−.
Pyramidalization is a distortion of this molecular shape towards a tetrahedral molecular geometry. One way to observe this distortion is in pyramidal alkenes.
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