Molecule Shapes
Add bonds and lone pairs. See the electron geometry and the molecular shape together.
Bent
This arrangement matches Water (H₂O).
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Bent
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Lone pairs
Electron shell
Bond angles
Polarity arrow
AX₂E₂
4 electron domains: 2 bonds and 2 lone pairs.
sp³
< 109.5°
103°
Polar
Lone pairs push the bonding electrons closer together. The electron geometry stays Tetrahedral, the atoms stay bent, and the bond angle falls below the ideal value.
How VSEPR builds a molecular shape
VSEPR is built on the repulsion of electron pairs in the valence shell. Bonds and lone pairs around the central atom stay as far apart as they can. That repulsion decides how the atoms are arranged.
Electron geometry counts bonds and lone pairs together. Molecular shape looks only at where the atoms sit. Hide the lone pairs and the atoms keep their arrangement. In water, four electron domains sit in a tetrahedron. Hide the two lone pairs and the molecular shape is bent.
A double bond and a triple bond each count as one electron domain. Carbon dioxide has two double bonds on carbon. The two domains sit opposite each other, so the molecule is linear.
VSEPR describes covalent molecules. An ionic solid does not get its own molecular shape. The ions take their arrangement from a unit cell repeated in three dimensions.
Frequently asked questions
What is the difference between electron geometry and molecular geometry?
Electron geometry counts bonds and lone pairs together. Molecular geometry looks only at where the atoms sit. In water, four electron domains form a tetrahedron. Hide the two lone pairs and the molecular shape is bent.
Why is the bond angle in water about 104.5 degrees?
Water has two bonds and two lone pairs on oxygen. Four electron domains would give a tetrahedral angle of 109.5 degrees. The lone pairs push the bonding electrons closer together, so the H–O–H angle closes to about 104.5 degrees and the molecule is bent.
Why is ammonia trigonal pyramidal?
Ammonia has three bonds and one lone pair on nitrogen. The four electron domains sit in a tetrahedron. The lone pair occupies one vertex, so the three hydrogens form a trigonal pyramid. The bond angle is about 107 degrees.
Does a double bond count as one electron domain?
Yes. A double bond and a triple bond each count as one electron domain. Carbon dioxide has two double bonds on carbon. The two domains sit opposite each other, so the molecule is linear.
Do ionic compounds have a molecular shape?
No. VSEPR describes covalent molecules. An ionic solid is not given its own molecular shape. The ions take their arrangement from a unit cell repeated in three dimensions.
Why is carbon dioxide linear?
Carbon dioxide has two double bonds on carbon and no lone pair on that atom. Each double bond counts as one domain, so two domains sit opposite each other. The molecular shape is linear and the bond angle is 180 degrees.