Author
Home > Science > What is the Difference Between Trigonal Planar and Trigonal Pyramidal?

Guilherme Mazui

•3 minutes to read

What is the Difference Between Trigonal Planar and Trigonal Pyramidal?

🆚 Go to Comparative Table 🆚

The main differences between trigonal planar and trigonal pyramidal molecular geometries are:

  1. Lone pair electrons: Trigonal planar geometry has no lone pair electrons on the central atom, while trigonal pyramidal geometry has one lone pair of electrons on the central atom.
  2. Bond angles: In trigonal planar geometry, the bond angles are around 120°, while in trigonal pyramidal geometry, the bond angles are less than 120°, typically around 107°.
  3. Plane: In trigonal planar geometry, all the atoms are located on one plane, while in trigonal pyramidal geometry, the atoms are not in one plane.
  4. Bond-lone pair repulsion: In trigonal pyramidal geometry, there is bond-bond and bond-lone pair repulsion, while in trigonal planar geometry, there is only bond-bond repulsion.

Examples of trigonal planar molecules include formaldehyde (CH2O) and some ions, such as the carbonate ion (CO32-). Examples of trigonal pyramidal molecules include ammonia (NH3), chlorate ion, and sulfite ion.

On this page
  • What is the Difference Between Trigonal Planar and Trigonal Pyramidal?
  • Comparative Table: Trigonal Planar vs Trigonal Pyramidal

    • Comparative Table: Trigonal Planar vs Trigonal Pyramidal

    The main differences between trigonal planar and trigonal pyramidal molecular geometries are as follows:

    Trigonal Planar Trigonal Pyramidal
    Three atoms surrounding the central atom have bond angles of 120 degrees. Bond angles between the central atom and the three surrounding atoms are less than 120 degrees, resulting in a three-dimensional shape.
    All the atoms lie on a single plane. The atoms are arranged in a pyramid shape, with the lone pair of electrons occupying the fourth position.
    No lone pair electrons at the central atom. The central atom has four hybridized orbitals, with three of the orbitals used to form sigma bonds with the other atoms and one of the orbitals containing a lone pair of electrons.
    Examples of trigonal planar molecules include formaldehyde (CH2O) and some ions, such as the carbonate ion (CO32-). Examples of trigonal pyramidal molecules include NH3 and some ions, such as NH4+.

    In summary, trigonal planar geometry has three atoms or groups arranged in a flat, triangular shape, while trigonal pyramidal geometry has three atoms or groups arranged in a three-dimensional pyramid shape with a lone pair of electrons at the apex.

    Read more:

    Guilherme Mazui

    Guilherme Mazui is graduated in journalism from the Federal University of Minas Gerais (UFMG) and a master's degree in Communication from the University of São Paulo (USP). In addition, he has experience in advertising writing and has worked as a content editor in several companies.