User:Unit388/LMGM - Lync’s Molecular Geometry Model

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Lync’s Molecular Geometry Model(LMGM), is a substitute for needing to construct a Lewis Dot Diagram in order to predict the molecular geometry of a given molecule using VSEPR Theory[1]. Being able to bypass the Lewis diagram can significantly reduce the prediction time.


= Total number of valence electrons
= Number of atoms(not including the center)
= Total number of lone electrons

There are two versions of the LMGM equation, one for when the molecule contains hydrogen, and one for when it does not. This is due to the first electron shell holding 2 electrons, while the others hold 8 electrons. [2]

Without Hydrogen:

With Hydrogen:

The result will be the total number of free electrons. The number of electron pairs is equal to your sum divided by two. This formula does not account for charge. Charge can be accounted for by simply adding for negative charges, and subtracting positive charges from the final answer.

Molecular Geometry[edit]

Once lone pairs have been calculated, the number of pairs and the total number of electron clouds can be used to identify 3D geometry.

Calculate 3D shape using lone pairs and electron clouds

See also[edit]


  • Jolly, W. L.,Modern Inorganic Chemistry, McGraw-Hill, 1984, p.77-90. ISBN 0-07-032760-2
  • Aronson, Lync. "LMGM". NZCHEM Publication. Retrieved 27 February 2015.