Trigonal planar molecular geometry
Trigonal planar is a molecular geometry model in chemistry where one central atom is bonded to three peripheral atoms located at the corners of an equilateral triangle, all lying in the same plane. This geometry is significant in both inorganic and organic chemistry, describing molecules such as boron trifluoride (BF3) and formaldehyde (H2CO), as well as ions like nitrate (NO−3) and carbonate (CO2−3).
- field
- Chemistry
- type
- Molecular geometry model
- point_group
- D3h
- examples
- BF3, H2CO, COCl2, SO3, NO−3, CO2−3, C(NH2)+3
- related_concepts
- AXE method, VSEPR theory, sp2 hybridization
Lore & Background
In the trigonal planar model, one central atom is surrounded by three atoms at the corners of an equilateral triangle, all in one plane. Molecules with non-identical ligands, such as formaldehyde (H2CO), deviate from this idealized geometry. Examples include boron trifluoride (BF3), phosgene (COCl2), and sulfur trioxide (SO3), as well as ions like nitrate (NO−3), carbonate (CO2−3), and guanidinium (C(NH2)+3).
Reader's Guide
Trigonal planar molecular geometry is a foundational concept in chemistry, describing the arrangement of atoms around a central atom in a flat, triangular configuration. It is central to understanding the structure and reactivity of many molecules and ions, including boron trifluoride and carbonate. In organic chemistry, planar three-connected carbon centers with trigonal planar geometry are often described as having sp2 hybridization. The geometry also appears in the transition state of nitrogen inversion, where pyramidal amines distort through a trigonal planar intermediate. Pyramidalization, a distortion toward tetrahedral geometry, can be observed in pyramidal alkenes. This model is closely related to the AXE method and VSEPR theory, which predict molecular shapes based on electron pair repulsion. Its study aids in predicting molecular polarity, reactivity, and spectroscopic properties.
Did You Know?
- Such species belong to the point group D3h.
- Nitrogen inversion involves a trigonal planar transition state.
- In organic chemistry, trigonal planar carbon centers are often described as having sp2 hybridization.
Frequently Asked Questions
Who is Trigonal planar molecular geometry?
Trigonal planar is a molecular geometry model in which a single central atom bonds to three surrounding atoms positioned at the vertices of an equilateral triangle, with every atom lying in one flat plane. It is the idealized shape VSEPR theory predicts when a central atom carries exactly three bonding pairs and zero lone pairs.
Why is Trigonal planar molecular geometry important?
It supplies the foundational shape for rationalizing electrophilic addition across alkenes, nucleophilic attack on carbonyls, and the symmetry of planar cations such as guanidinium. Without this model, predicting stereochemical outcomes and reactivity patterns across both organic and inorganic chemistry would be far less precise.
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