What is VSEPR theory and how does it predict molecular geometry?

VSEPR (Valence Shell Electron Pair Repulsion) theory predicts 3D molecular shapes by assuming electron pairs around a central atom repel each other and arrange to maximize distance. Count bonding pairs and lone pairs, determine the electron geometry, then remove lone pairs to get the molecular geometry. For example, water has 4 electron pairs (2 bonding, 2 lone) giving tetrahedral electron geometry but bent molecular shape with 104.5 degree bond angle.

How does the 3D molecular viewer work?

The tool fetches real 3D atomic coordinates from the PubChem database and renders them using WebGL-based 3Dmol.js. You can rotate the model by dragging, zoom with scroll, and pan with right-drag. Lone pairs are shown as translucent golden lobes positioned using VSEPR geometry. Bond angle measurements are displayed directly on the 3D model. If PubChem data is unavailable, the tool falls back to mathematically computed VSEPR positions.

What is the difference between electron geometry and molecular geometry?

Electron geometry considers ALL electron pairs (bonding plus lone pairs) around the central atom. Molecular geometry only considers the positions of atoms (bonding pairs). For NH3, electron geometry is tetrahedral (4 electron pairs total) but molecular geometry is trigonal pyramidal (3 bonding pairs visible, 1 lone pair invisible). The 3D viewer shows both: atoms as colored spheres and lone pairs as translucent golden lobes.

Can I compare two molecules side by side?

Yes. Click the Compare tab and enter two formulas or molecule names. The tool renders both molecules in interactive 3D viewers side by side and shows a comparison table highlighting matching and differing properties including geometry, bond angle, hybridization, bonding pairs, and lone pairs. Try presets like H2O vs NH3 or CH4 vs CCl4 to see how substituents affect molecular shape.

What are the main molecular geometry shapes in VSEPR theory?

The main shapes are: Linear (180 degrees, e.g. CO2), Bent (104-120 degrees, e.g. H2O), Trigonal Planar (120 degrees, e.g. BF3), Trigonal Pyramidal (107 degrees, e.g. NH3), Tetrahedral (109.5 degrees, e.g. CH4), See-Saw (e.g. SF4), T-Shaped (e.g. ClF3), Square Planar (90 degrees, e.g. XeF4), Square Pyramidal (e.g. BrF5), Trigonal Bipyramidal (90 and 120 degrees, e.g. PCl5), and Octahedral (90 degrees, e.g. SF6). All shapes can be explored in interactive 3D on this tool.

Can this tool handle complex molecules like glucose or benzene?

Yes. For multi-center molecules like glucose (C6H12O6), ethanol (C2H6O), or benzene (C6H6), the tool fetches the full 3D structure from PubChem and renders it as an interactive model. It also analyzes each atom center individually using VSEPR theory, showing geometry, bond angles, and hybridization per center, plus the Index of Hydrogen Deficiency (IHD) to identify rings and double bonds.

3D Molecular Geometry Calculator

Chemical Formula

Enter a formula (CH4, NH3, SF6, NH4+) or molecule name (Methane, Water, Ammonia).

Bonding Pairs (BP)

Lone Pairs (LP)

Atoms bonded to central atom (BP) and lone electron pairs (LP)

Quick Examples

Molecular Geometry

⚛

Enter molecule details

Determine molecular geometry using VSEPR theory with step-by-step analysis.

Compare Molecules

Molecule Database (54)

Formula	Name	BP	LP	Geometry	Angle

Also try → ✍ Molecule Draw NEW 🔗 Lewis Structure Generator

1 What is VSEPR Theory?

VSEPR (Valence Shell Electron Pair Repulsion) theory states that electron pairs repel each other whether they are bonding pairs or lone pairs. They position themselves around a central atom to minimize repulsion, which determines the 3D shape of the molecule. An electron group can be a bond pair, lone pair, single unpaired electron, or multiple bond.

Central Atom

X_n

Bonding Pairs

E_m

Lone Pairs

Shape

💡

Two critical concepts: Electron-group geometry is determined solely by the number of electron groups around the central atom. Molecular geometry depends on both electron groups AND how many are lone pairs. They only match when there are zero lone pairs.

2 How to Determine Molecular Geometry

Follow these four steps for any molecule. This is the exact process our calculator automates:

Draw the Lewis Structure

H — O — H

2 bonding pairs 2 lone pairs

O is central (6 e⁻), each H has 1 e⁻. Total: 8 valence electrons.

Count Electron Groups

⎯Bond

∷LP

= 4 electron groups

Each bond or lone pair = 1 group. Double/triple bonds count as one group.

Electron Geometry → Tetrahedral

2 groups→Linear

3 groups→Trig. Planar

4 groups→Tetrahedral

5 groups→Trig. Bipyramidal

6 groups→Octahedral

4 electron groups arrange at tetrahedral corners (109.5°).

Remove Lone Pairs → Bent!

: : O H H

Tetrahedral
(electron)

× LP ⇒

H H

Bent
104.5°

AX₂E₂ → Bent. Lone pairs compress bond angle from 109.5° to 104.5°.

3 Electron Geometry vs Molecular Geometry

This is the most common point of confusion. Both start from the same electron arrangement, but molecular geometry only shows where atoms sit — lone pairs are invisible to the eye.

Example: Ammonia (NH₃) — AX₃E

Electron Geometry

: | H—N—H | H

Tetrahedral
4 electron groups (3 bonds + 1 lone pair) arrange tetrahedrally

→

Molecular Geometry

H—N—H | H

Trigonal Pyramidal
Remove the lone pair — only 3 atoms remain in a pyramid shape

Example: Water (H₂O) — AX₂E₂

Electron Geometry

: : | H—O—H

Tetrahedral
4 electron groups (2 bonds + 2 lone pairs)

→

Molecular Geometry

H—O—H

Bent
Two lone pairs hidden — only the V-shape remains at 104.5°

4 Complete VSEPR Reference Table

Every electron group count mapped to its electron geometry, molecular geometry, and bond angle. This is the master table used by chemists worldwide.

Groups	Electron Geometry	LP	VSEPR	Molecular Shape	Bond Angle	Example
2 Electron Groups
2	Linear	0	AX₂	Linear	180°	CO₂, BeCl₂
3 Electron Groups
3	Trigonal Planar	0	AX₃	Trigonal Planar	120°	BF₃, SO₃
3	Trigonal Planar	1	AX₂E	Bent	~119°	SO₂, O₃
4 Electron Groups
4	Tetrahedral	0	AX₄	Tetrahedral	109.5°	CH₄, CCl₄
4	Tetrahedral	1	AX₃E	Trigonal Pyramidal	~107°	NH₃, PCl₃
4	Tetrahedral	2	AX₂E₂	Bent	~104.5°	H₂O, H₂S
5 Electron Groups
5	Trigonal Bipyramidal	0	AX₅	Trigonal Bipyramidal	90°, 120°	PCl₅, PF₅
5	Trigonal Bipyramidal	1	AX₄E	See-Saw	~102°, ~173°	SF₄, TeCl₄
5	Trigonal Bipyramidal	2	AX₃E₂	T-Shaped	~87.5°	ClF₃, BrF₃
5	Trigonal Bipyramidal	3	AX₂E₃	Linear	180°	XeF₂, I₃⁻
6 Electron Groups
6	Octahedral	0	AX₆	Octahedral	90°	SF₆, PF₆⁻
6	Octahedral	1	AX₅E	Square Pyramidal	~84°	BrF₅, IF₅
6	Octahedral	2	AX₄E₂	Square Planar	90°	XeF₄, ICl₄⁻
7 Electron Groups
7	Pentagonal Bipyramidal	0	AX₇	Pentagonal Bipyramidal	72°, 90°	IF₇

5 How Lone Pairs Compress Bond Angles

Lone pairs are held closer to the nucleus than bonding pairs, so they occupy more angular space. This extra repulsion pushes bonding pairs closer together, compressing the bond angle. Each lone pair reduces the angle by roughly 2–3°.

Tetrahedral family — bond angle compression

CH₄ (0 LP)

109.5°

ideal

NH₃ (1 LP)

107°

−2.5°

H₂O (2 LP)

104.5°

−5°

Repulsion strength order

LP–LP > LP–BP > BP–BP (strongest → weakest)

💡

Why this order? Lone pairs spread out more because they are attracted to only one nucleus (the central atom). Bonding pairs are shared between two nuclei, which keeps them more tightly confined.

6 Common Molecular Geometries

The most common VSEPR shapes with bond angles, hybridization, and lone pair positions:

VSEPR molecular geometry shapes diagram showing Linear CO2, Trigonal Planar BF3, Bent H2O with lone pairs, Tetrahedral CH4, Trigonal Pyramidal NH3, Trigonal Bipyramidal PCl5, Octahedral SF6, and See-Saw SF4 with bond angles and hybridization

Quick reference cards:

● Linear (AX₂)

180° • sp • CO₂, BeCl₂, HCN

● Trigonal Planar (AX₃)

120° • sp² • BF₃, SO₃, AlCl₃

● Tetrahedral (AX₄)

109.5° • sp³ • CH₄, CCl₄, SiH₄

● Bent (AX₂E / AX₂E₂)

104–120° • sp² or sp³ • H₂O, SO₂, O₃

● Trigonal Pyramidal (AX₃E)

~107° • sp³ • NH₃, PCl₃, AsH₃

● Octahedral (AX₆)

90° • sp³d² • SF₆, PF₆⁻

7 Understanding Hybridization

Hybridization describes how atomic orbitals mix to form new hybrid orbitals for bonding. The total number of electron domains (bonding + lone pairs) determines the hybridization type.

2 domains → sp

Two hybrid orbitals at 180°. Linear. Examples: CO₂, BeCl₂, HCN.

3 domains → sp²

Three hybrid orbitals at 120°. Trigonal planar. Examples: BF₃, SO₂, O₃.

4 domains → sp³

Four hybrid orbitals at 109.5°. Tetrahedral. Examples: CH₄, NH₃, H₂O.

5 domains → sp³d

Five hybrid orbitals at 90° & 120°. Trigonal bipyramidal. Examples: PCl₅, SF₄.

6 domains → sp³d²

Six hybrid orbitals at 90°. Octahedral. Examples: SF₆, XeF₄.

👉

Quick rule: Count the total number of electron pairs (bonding + lone) around the central atom. That count equals the number of hybrid orbitals needed: 2→sp, 3→sp², 4→sp³, 5→sp³d, 6→sp³d².

8 Polarity & Dipole Moments

Molecular geometry directly determines whether a molecule is polar or nonpolar. When electrons are not distributed equally, the molecule has a net dipole moment (μ = δ × d). Electronegativity differences between atoms create partial charges (δ+ and δ−).

Nonpolar

O=C=O

CO₂ is linear — two equal C=O dipoles point in opposite directions and cancel out. Net dipole = 0.

Polar

H—O—H

H₂O is bent — the two O–H dipoles point in similar directions and do not cancel. Net dipole ≠ 0.

Quick Polarity Rules

No lone pairs on central atom + all identical terminal atoms = nonpolar (e.g., CH₄, BF₃, SF₆)

Symmetric geometry can still be nonpolar even with polar bonds — dipoles cancel by symmetry (e.g., CO₂ linear, XeF₄ square planar)

Lone pairs on the central atom almost always make the molecule polar (e.g., NH₃, H₂O, SF₄)

9 Why Molecular Geometry Matters

Molecular shape determines physical and chemical properties, from boiling points to biological activity.

Drug Design

Pharmaceutical molecules must have the right 3D shape to bind to protein targets. Geometry determines whether a drug fits its receptor like a key in a lock.

Polarity & Solubility

CO₂ is linear and nonpolar (dissolves in oil), while H₂O is bent and highly polar (universal solvent). Same atoms, different geometry, different properties.

Material Science

Silicon’s tetrahedral bonding (sp³) creates the diamond cubic crystal structure that makes semiconductor chips possible.

Biological Activity

Enzyme active sites recognize substrates by their exact 3D shape. A single bond angle difference can make a molecule biologically inactive or toxic.

Frequently Asked Questions

Electron geometry considers all electron pairs (bonding + lone) while molecular geometry only considers atom positions. For example, NH₃ has tetrahedral electron geometry (4 total pairs) but trigonal pyramidal molecular geometry (3 visible bonds). They match only when there are zero lone pairs on the central atom.

The central atom is usually the least electronegative atom (excluding hydrogen, which is always terminal). In most formulas, the central atom is written first: C in CH₄, N in NH₃, S in SF₆. For oxoacids, the non-oxygen non-hydrogen atom is central (S in H₂SO₄).

Lone pairs are held closer to the nucleus than bonding pairs, so they occupy more angular space. This extra repulsion compresses the bond angles. The repulsion order is: LP–LP > LP–BP > BP–BP. Each lone pair reduces bond angles by roughly 2–3° from the ideal geometry. That is why water (2 lone pairs) has 104.5° instead of 109.5°.

First determine the molecular geometry. If the molecule is perfectly symmetric with identical terminal atoms and no lone pairs (like CH₄, CO₂, SF₆), it is nonpolar because dipoles cancel. If there are lone pairs on the central atom or different terminal atoms, the molecule is usually polar (like H₂O, NH₃, CHCl₃). The key is whether individual bond dipoles cancel by symmetry.

The database contains 54 molecules covering all VSEPR geometries from linear to pentagonal bipyramidal. The dynamic formula parser handles any molecule built from known elements (H through Rn), including multi-center molecules like glucose (C₆H₁₂O₆) and ethanol (C₂H₆O). It supports ions with + or − charge notation (NH4+, SO4(2-)). Enter the central atom first in the formula for best results.

Yes, 100% free with no signup. Features include VSEPR analysis by electron pairs or formula, 54-molecule database, step-by-step analysis, downloadable PDF results, printable VSEPR reference charts, practice worksheets for teachers, multi-center molecule support, and shareable URLs. All computation runs in your browser.

Yes. For multi-center molecules like glucose (C₆H₁₂O₆), ethanol (C₂H₆O), or benzene (C₆H₆), the calculator detects multiple atom centers and analyzes each one using VSEPR theory. It shows geometry, bond angles, and hybridization per atom type, plus the Index of Hydrogen Deficiency (IHD) for rings and double bonds.

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Molecular Geometry

Enter molecule details

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Molecule Database (54)

1 What is VSEPR Theory?

2 How to Determine Molecular Geometry

Draw the Lewis Structure

Count Electron Groups

Electron Geometry → Tetrahedral

Remove Lone Pairs → Bent!

3 Electron Geometry vs Molecular Geometry

Example: Ammonia (NH₃) — AX₃E

Electron Geometry

Molecular Geometry

Example: Water (H₂O) — AX₂E₂

Electron Geometry

Molecular Geometry

4 Complete VSEPR Reference Table

5 How Lone Pairs Compress Bond Angles

6 Common Molecular Geometries

● Linear (AX₂)

● Trigonal Planar (AX₃)

● Tetrahedral (AX₄)

● Bent (AX₂E / AX₂E₂)

● Trigonal Pyramidal (AX₃E)

● Octahedral (AX₆)

7 Understanding Hybridization

2 domains → sp

3 domains → sp²

4 domains → sp³

5 domains → sp³d

6 domains → sp³d²

8 Polarity & Dipole Moments

Nonpolar

Polar

Quick Polarity Rules

9 Why Molecular Geometry Matters

Drug Design

Polarity & Solubility

Material Science

Biological Activity

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