The molecular geometry of a molecule can be determined using the VSEPR theory.
VSEPR (Valence Shell Electron Pair Repulsion) Theory: The basic premise of this simple theory is that electron pairs (bonding and nonbonding) repel one another; so the electron pairs will adopt a geometry about an atom that minimizes these repulsions. Use the method below to determine the molecular geometry about an atom.
Write the Lewis dot structure for the molecule.
Count the number of things (atoms, groups of atoms, and lone pairs of electrons) that are directly attached to the central atom (the atom of interest) to determine the overall (electronic) geometry of the molecule.
Now ignore the lone pairs of electrons to get the molecular geometry of the molecule. The molecular geometry describes the arrangement of the atoms only and not the lone pairs of electrons. If there are no lone pairs in the molecule, then the overall geometry and the molecular geometry are the same. If the overall geometry is tetrahedral, then there are three possibilities for the molecular geometry; if it is trigonal planar, there are two possibilities; and if it is linear, the molecular geometry must also be linear. The diagram below illustrates the relationship between overall (electronic) and molecular geometries. To view the geometry in greater detail, simply click on that geometry in the graphic below. Although there are many, many different geometries that molecules adopt, we are only concerned with the five shown below.
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Linear
a square
Molecular geometry will be bent, electron geometry will be trigonal planar
plane triangle
The only possible geometry of a diatomic molecule such as P2 is linear.
The molecular geometry of a nitrogen molecule is linear.
Bent
The electron geometry of a water molecule is tetrahedral even though the molecular geometry is _____. Bent
One way to determine the molecular geometry of a molecule without using a Lewis structure is by using the VSEPR theory. This theory helps predict the shape of a molecule based on the arrangement of its atoms and lone pairs. By considering the number of bonding pairs and lone pairs around the central atom, you can determine the molecular geometry.
Check the molecular geometry to determine if the molecule is asymmetrical. If the molecule has a symmetrical shape, it is likely nonpolar. If it is asymmetrical, check for polar bonds and the overall molecular polarity.
The molecular geometry of the CF3H molecule, based on its Lewis structure, is trigonal pyramidal.
Linear
a square
The molecular geometry of a molecule with the keyword "bro3" according to the VSEPR theory is trigonal pyramidal.
Molecular geometry will be bent, electron geometry will be trigonal planar
plane triangle
The only possible geometry of a diatomic molecule such as P2 is linear.