VSEPR Geometry Finder

Results

• 109.5° ideal, slightly smaller in practice because lone pairs take up more room than bonding pairs
• Polarity: Polar if the A–X bonds are polar: the shape is not symmetric, so the bond dipoles do not cancel. A guide only. It needs polar A–X bonds, so check the electronegativity difference.
• Examples: H₂O, H₂S, OF₂

How to Use the VSEPR Geometry Finder

1. 1. Draw the Lewis structure first. The tool needs two counts from it: how many atoms are bonded to the central atom, and how many lone pairs sit on the central atom itself.
2. 2. Enter the counts. Pick the bonded atoms (X) and lone pairs (E), or type the AXE notation directly — AX3E means three bonded atoms and one lone pair. The two inputs stay in step with each other.
3. 3. Read the shape. The result gives the molecular shape, the electron geometry it comes from, the ideal bond angles, the hybridization label and a polarity hint. The table below lists every shape with the same steric number so you can see where yours sits.
4. 4. Turn the model. Drag the slider to rotate the 3-D drawing. Lone pairs are shown as dashed lobes, so you can see which corners of the electron geometry are empty.

How VSEPR Works

Valence-shell electron-pair repulsion theory says that the electron domains around a central atom — each bonded atom and each lone pair — repel one another and settle as far apart as possible. A single, double or triple bond counts as one domain, because all its electrons occupy the same region between two nuclei. The steric number is the number of domains, and it fixes the electron geometry: linear for 2, trigonal planar for 3, tetrahedral for 4, trigonal bipyramidal for 5 and octahedral for 6.

The molecular shape describes only where the atoms are, so a lone pair shapes the molecule without being seen in it. Water has four domains and so a tetrahedral electron geometry, but with two of the corners occupied by lone pairs the atoms form a bent shape. Lone pairs also take up more room than bonding pairs — the repulsion order is lone pair–lone pair, then lone pair–bonding pair, then bonding pair–bonding pair — which squeezes the real bond angles below the ideal ones.

Counting Domains: Worked Examples

• Water, H₂O. Oxygen has 6 valence electrons; two are used in the two O–H bonds, leaving 4 electrons, which is 2 lone pairs. That is AX₂E₂: tetrahedral electron geometry, bent shape. The ideal angle is 109.5°, and the measured H–O–H angle is about 104.5°.
• Ammonia, NH₃. Nitrogen has 5 valence electrons; three go into N–H bonds, leaving 2 electrons, or 1 lone pair. That is AX₃E: trigonal pyramidal, with H–N–H close to 107°.
• Sulfur tetrafluoride, SF₄. Sulfur has 6 valence electrons; four go into S–F bonds, leaving 2 electrons, one lone pair. That is AX₄E: five domains, so trigonal bipyramidal electron geometry, with the lone pair in an equatorial position and a seesaw shape.
• Xenon tetrafluoride, XeF₄. Xenon has 8 valence electrons; four go into Xe–F bonds, leaving 4, or 2 lone pairs. That is AX₄E₂: octahedral electron geometry with the lone pairs opposite each other, so the four fluorines lie in one plane — square planar.
• Carbon dioxide, CO₂. Each C=O double bond is one domain, and carbon has no lone pair, so CO₂ is AX₂ and linear.

Polarity and Hybridization

A molecule is polar when its bond dipoles do not cancel. In a symmetric shape — linear AX₂, trigonal planar AX₃, tetrahedral AX₄, trigonal bipyramidal AX₅, octahedral AX₆, square planar AX₄E₂ and linear AX₂E₃ — identical outer atoms make the dipoles cancel, so CO₂, BF₃, CH₄ and SF₆ are nonpolar. Bent, pyramidal, seesaw, T-shaped and square pyramidal shapes are not symmetric, so molecules like H₂O, NH₃ and SF₄ are polar when their bonds are. Replace one outer atom with a different one, as in CH₃Cl, and even a symmetric shape becomes polar. The tool's polarity line is therefore a guide that depends on your tick-box answer about the outer atoms; it needs polar bonds to begin with.

The hybridization label follows the steric number: 2 domains is sp, 3 is sp², 4 is sp³, 5 is sp³d and 6 is sp³d². The sp, sp² and sp³ labels are a sound description of the σ framework. The d-orbital labels for five and six domains are a textbook convention; modern calculations find that d orbitals contribute little to bonding in molecules such as SF₆, so treat sp³d and sp³d² as names for the geometry rather than proof of d-orbital use.

What VSEPR Cannot Do

• It is qualitative. It predicts the shape and the direction of angle changes, not exact angles. Larger outer atoms, double bonds and electronegativity differences all shift angles by a few degrees.
• It works best for main-group centres. Transition-metal complexes and some heavy main-group compounds, such as gaseous calcium and strontium difluoride, are bent where VSEPR predicts linear.
• It stops at six domains here. Seven-domain shapes such as IF₇ (pentagonal bipyramidal) exist but are beyond a standard course, and a few six-domain combinations such as AX₃E₃ have no stable main-group examples, so the tool leaves them unnamed.

Frequently Asked Questions

What is the difference between electron geometry and molecular geometry?

Electron geometry describes how all the electron domains, bonding and non-bonding, are arranged around the central atom. Molecular geometry describes only the positions of the atoms. They are the same when there are no lone pairs; with lone pairs they differ, so water is tetrahedral in electron geometry and bent in molecular geometry.

How do you find the VSEPR shape of a molecule?

Draw the Lewis structure, count the atoms bonded to the central atom (X) and the lone pairs on it (E), and add them for the steric number. That number gives the electron geometry, and the pattern of X and E gives the molecular shape — for example AX₃E is trigonal pyramidal. Double and triple bonds count as one bonded atom.

Why is water bent while carbon dioxide is linear?

Oxygen in water has two bonded atoms and two lone pairs, four domains in all, which point to the corners of a tetrahedron, leaving a bent molecule. Carbon in CO₂ has two double bonds and no lone pairs, so only two domains, which sit 180° apart.

Do double and triple bonds count as one electron domain?

Yes. All the electrons in a multiple bond lie in the same region between the two nuclei, so VSEPR treats the bond as a single domain. Formaldehyde, H₂C=O, is therefore AX₃ and trigonal planar, with angles close to 120°.

Why do lone pairs go in the equatorial positions of a trigonal bipyramid?

An equatorial position has two neighbours at 90°, an axial one has three, so a lone pair — which repels more strongly than a bonding pair — has less repulsion in the equatorial plane. This is why SF₄ is a seesaw, ClF₃ is T-shaped and XeF₂ is linear.

How do you get hybridization from the steric number?

Use the number of electron domains on the central atom: 2 gives sp, 3 gives sp², 4 gives sp³, 5 gives sp³d and 6 gives sp³d². Lone pairs count as domains, so ammonia, with four, is sp³ even though only three orbitals form bonds.

Is a molecule with a symmetric shape always nonpolar?

No. It is nonpolar only when the outer atoms are identical, so the bond dipoles cancel. CCl₄ is nonpolar, but CHCl₃ has the same tetrahedral shape and is polar. Check the shape and whether the outer atoms are all the same.