VSEPR Shape Visualizer

Build and explore 3D molecular shapes based on VSEPR theory.

Controls

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Examples:
Electron Geometry
Tetrahedral
Molecular Shape
Tetrahedral
Example
CH₄
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Prerequisite: Lewis Structures

To use this tool, you must know how to find the bonding and lone pairs for a molecule by drawing its Lewis Structure.

Learn How →

How to Use This Tool: An Example with Water (H₂O)

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Identify the Pairs

Draw the Lewis structure for water. You'll see the central Oxygen atom has 2 bonding pairs (with H) and 2 lone pairs.

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2

Set the Sliders

Use the controls above. Set "Bonding Pairs" to 2 and "Lone Pairs" to 2. The visualizer will update instantly.

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Observe the "Aha!" Moment

The Electron Geometry is Tetrahedral (4 domains), but the Molecular Shape is Bent due to the pushy lone pairs!

Understanding the Preset Examples

CO₂ (Carbon Dioxide)

Valence e⁻: 4 (from C) + 2×6 (from O) = 16. After forming two C=O double bonds to satisfy Carbon's octet, the central Carbon is bonded to two atoms.

Result: 2 Bonding Pairs, 0 Lone Pairs

H₂O (Water)

Valence e⁻: 2×1 (from H) + 6 (from O) = 8. After forming two H-O single bonds (using 4 e⁻), the remaining 4 electrons are placed on the central Oxygen as two lone pairs.

Result: 2 Bonding Pairs, 2 Lone Pairs

CH₄ (Methane)

Valence e⁻: 4 (from C) + 4×1 (from H) = 8. Carbon forms four single bonds with the four Hydrogen atoms, using all 8 electrons. There are no electrons left for lone pairs on the central atom.

Result: 4 Bonding Pairs, 0 Lone Pairs

NH₃ (Ammonia)

Valence e⁻: 5 (from N) + 3×1 (from H) = 8. Nitrogen forms three single bonds with Hydrogen (using 6 e⁻). The remaining 2 electrons form one lone pair on the central Nitrogen.

Result: 3 Bonding Pairs, 1 Lone Pair

BF₃ (Boron Trifluoride)

Valence e⁻: 3 (from B) + 3×7 (from F) = 24. Boron forms three single bonds with Fluorine. Boron is an exception to the octet rule and is stable with 6 electrons, so it has no lone pairs.

Result: 3 Bonding Pairs, 0 Lone Pairs

How It Works: The Rule of Repulsion

VSEPR (Valence Shell Electron Pair Repulsion) theory is a model used to predict the 3D geometry of molecules. The core idea is simple: electron pairs in the outer shell of a central atom repel each other. They arrange themselves in 3D space to be as far apart as possible, which minimizes this repulsion.

Bonding Pairs vs. Lone Pairs: What's the Difference?

This is the most important concept in VSEPR! The sliders above let you control two types of electron pairs.

  • A Bonding Pair is a pair of electrons shared between the central atom and another atom. It forms the actual chemical bond you can see.
  • A Lone Pair is a pair of electrons that belongs only to the central atom and is not involved in a bond. Think of it as an invisible, but very pushy, cloud of negative charge.

Because lone pairs aren't "tied down" between two atoms, they take up more space and repel other electron pairs more strongly than bonding pairs do. This is the key to understanding why molecular shapes change!

Important: While outer atoms can have lone pairs (like the oxygens in CO₂), VSEPR theory focuses only on the electron domains around the central atom to determine the overall molecular shape. That's why our sliders only control the lone pairs on the central atom.

Frequently Asked Questions

What's the difference between Electron Geometry and Molecular Shape?

Electron Geometry describes the arrangement of all electron domains (both bonding and lone pairs) around the central atom. Molecular Shape (or molecular geometry) describes the arrangement of only the atoms. If there are no lone pairs on the central atom, the two geometries are the same. If there are lone pairs, they influence the shape but are not included in the final shape's name.

Why are the bond angles in NH₃ and H₂O smaller than the ideal 109.5°?

Lone pairs are more repulsive than bonding pairs because they are not confined between two atoms and take up more space. In ammonia (NH₃), the single lone pair pushes the three N-H bonds closer together, reducing the angle to ~107°. In water (H₂O), the two lone pairs exert an even stronger repulsion, compressing the H-O-H angle to ~104.5°.

How do double or triple bonds count in VSEPR theory?

For VSEPR purposes, a double bond or a triple bond is treated as a single electron domain, just like a single bond. The multiple pairs of electrons in a double/triple bond are all located in the same region between the two atoms, so they act as one "super-pair" that repels other domains. For example, in CO₂, the C=O double bonds are treated as two domains, resulting in a linear shape.