VSEPR Theory: Definition, Table, Chart, Formula, Examples, Questions

Edited By Shivani Poonia | Updated on Jul 02, 2025 07:57 PM IST

According to this theory, electron pairs around a central atom will arrange themselves as far apart as possible to minimize repulsion. VSEPR considers both bonding electron pairs—pairs of electrons that are involved in the formation of bonds—and lone pairs of electrons that do not participate in bonding when predicting the geometry of a molecule. The common molecular geometries that result from VSEPR include linear, trigonal planar, tetrahedral, trigonal bipyramidal, and octahedral.

VSEPR Theory: Definition, Table, Chart, Formula, Examples, Questions

VSEPR Theory

Valence shell electron-pair repulsion theory (VSEPR theory) enables us to predict the molecular structure, including approximate bond angles around a central atom of a molecule from the estimation of the number of bonds and lone pairs of electrons in its Lewis structure.

The main postulates of VSEPR theory are:

The actual shape of a molecule depends upon the number of electron pairs (bonded or non–bonded) around the central atom.
The electron pairs tend to repel each other due to their negative charge.
Electron pairs arrange themselves in such a way that there exists a minimum repulsion between them.
The valence shell is considered as a sphere with the electron pairs placed at a distance.
A multiple bond is treated as if it is a single electron pair & the electron pairs that constitute the bond as a single pair.
The repulsive interaction of electron pairs decreases in the order as mentioned below:

Lone pair (lp) – Lone pair (lp) > Lone pair (lp) – Bond pair (bp) > Bond pair (bp) – Bond pair (bp).

Double bonds cause more repulsion than single bonds, and triple bonds cause more repulsion than double bonds. This repulsion decreases sharply with increasing bond angle between the electron pairs.

Let us understand VSEPR theory using a gaseous BeF₂ molecule. In the Lewis structure of BeF₂ as shown in the figure, there are only two electron pairs around the central beryllium atom. With two bonds and no lone pairs of electrons on the central atom, the bonds are as far apart as possible, and the electrostatic repulsion between these regions of high electron density is reduced to a minimum when they are on opposite sides of the central atom, thus the bond angle is 180°.

A Lewis structure is shown. A fluorine atom with three lone pairs of electrons is single bonded to a beryllium atom which is single bonded to a fluorine atom with three lone pairs of electrons. The angle of the bonds between the two fluorine atoms and the beryllium atom is labeled, “180 degrees.”

The BeF₂ molecule adopts a linear structure in which the two bonds are at maximum distance from each other and maintain an angle of 180°.

As given in the table below, two regions of electron density around a central atom in a molecule form a linear geometry, three regions form a trigonal planar geometry, four regions form a tetrahedral geometry, five regions form a trigonal bipyramidal geometry, and six regions form an octahedral geometry.

Some Solved Examples

Example 1: The molecule having smallest bond angle is :

1)NCl₃

2)AsCl₃

3) SbCl₃

4)PCl₃

Solution

As we discussed in the concept

VSEPR Theory -

1. The shape of the molecule is determined by repulsions between all of the electron pairs present in the valence shell.

2. Order of repulsion

lone pair - Lone pair > Lone pair - Bond pair > Bond pair - bond pair

3 Repulsion among the bond pair is directly proportional to the bond order and electronegativity difference between the central atom and the other atom.

As we move down the group the size of the atom increases and as the size of the central atom increases lone pair-bond pair repulsion also increases. Thus bond angle decreases.

Increasing order of atomic radius:
N<P<As<Sb

Decreasing order of bond angle :
NCl3>PCl3>AsCl3>SbCl3

Hence, the answer is the option (3).

Example 2: The correct order of bond angles (smallest first ) in H2 S,NH3,BF3, and SiH4 is
1) H2 S<SiH4<NH3<BFF3
2) NH3<H2 S<SiH4<BF3
3) H2 S<NH3<SiH4<BF3
4) H2 S<NH3<BF3<SiH4

Solution

The correct order of bond angle ( smallest first )is
H2S<NH3<SiH4<BF392.6∘<107∘<109∘28′<120∘

Bond angle order = H₂S < NH₃< SiH₄< BF₃

Example 3: The type of hybridization and number of lone pair (s) of electrons of Xe in XeOF₄ respectively, are :

1) sp3d2 and 1
2) sp3d and 2
3) sp3d2 and 2
4) sp3d and 1

Solution

As we have learnt in Hybridisation:

Hybridization is sp³d²

It contains 5 sigma bonds and 1 pi bond.

It has 1 lone pair of electrons.

Hence, the correct answer is Option (1)

Example 4: The shape of a molecule is determined by

1)Valence bond theory

2)Molecular orbital theory

3) Valence shell electron pair repulsion theory

4)None

Solution

VSEPR (Valence Shell Electron Pair Repulsion) Theory - Valence shell electron-pair repulsion theory (VSEPR theory) enables us to predict the molecular structure, including approximate bond angles around a central atom of a molecule from the estimation of the number of bonds and lone pairs of electrons in its Lewis structure. The shape of a molecule depends upon the number of valence shell electron pairs (bonded or non-bonded) around the central atom. These pairs of electrons in the valence shell repel one another since their electron clouds are negatively charged.
Hence, the answer is the option (3).

Example 5: The reason for the change in bond angle in the different molecules having the same hybridization is given by:

1)Molecular orbital theory

2) Valence shell electron pair repulsion theory.

3)Valence bond theory

4)None

Solution

1. Electron pairs are always repelling each other and try to remain far apart

2. Different electron pairs have different orders of repulsion: L.P-L.P > L.P-B.P > B.P-B.P

3. If lone pairs are not present then geometry is equal to shape else geometry is not equal to the shape.

This all is explained by V.S.E.P.R. theory.
Hence, the answer is the option (2).

Summary

The Valence Shell Electron Pair Repulsion is one of the primary models used in computing the geometry of molecules, given electron pair repulsion. It was developed by Gillespie and Nyholm. The theory postulates that electron pairs around a central atom arrange themselves as far away from each other as possible, thereby minimizing the repulsion and thus determining the shape of the molecule. The theory describes all geometries of the molecules by considering both bonding and lone pairs of electrons.

Frequently Asked Questions (FAQs)

1. What is VSEPR theory and why is it important in chemistry?

VSEPR (Valence Shell Electron Pair Repulsion) theory is a model used to predict the shapes of molecules based on the arrangement of electron pairs around a central atom. It's important because molecular geometry affects a compound's properties, reactivity, and behavior in chemical reactions.

2. How does VSEPR theory explain the bent shape of a water molecule?

VSEPR theory explains that the bent shape of a water molecule results from the repulsion between the two bonding pairs and two lone pairs of electrons around the central oxygen atom. This repulsion causes the bonds to bend away from each other, creating a 104.5° angle between them.

3. What is the difference between electron domain geometry and molecular geometry?

Electron domain geometry considers all electron pairs (bonding and lone pairs) around the central atom, while molecular geometry only considers the arrangement of atoms. For example, in ammonia (NH3), the electron domain geometry is tetrahedral, but the molecular geometry is trigonal pyramidal due to the presence of a lone pair.

4. How does VSEPR theory account for lone pairs of electrons?

VSEPR theory considers lone pairs as electron domains that contribute to repulsion but don't appear in the molecular geometry. Lone pairs occupy more space than bonding pairs and can distort molecular shapes, often leading to smaller bond angles and asymmetrical structures.

5. What is the AXE notation in VSEPR theory, and how is it used?

AXE notation is used in VSEPR theory to describe molecular geometry, where A is the central atom, X is the number of bonded atoms, and E is the number of lone pairs. For example, AX3E1 represents a molecule with three bonded atoms and one lone pair, like ammonia (NH3).

6. Why does a molecule with four electron domains around the central atom adopt a tetrahedral shape?

A molecule with four electron domains adopts a tetrahedral shape because this arrangement minimizes repulsion between the electron pairs. The tetrahedral geometry allows for maximum separation (109.5° angles) between electron domains, resulting in the most stable configuration.

7. How does VSEPR theory explain the linear shape of carbon dioxide (CO2)?

VSEPR theory explains the linear shape of CO2 by considering that there are two bonding pairs and no lone pairs around the central carbon atom. To minimize repulsion, these two bonding pairs arrange themselves 180° apart, resulting in a linear molecule.

8. What factors can cause deviations from ideal VSEPR geometries?

Factors that can cause deviations from ideal VSEPR geometries include:

9. How does VSEPR theory explain the trigonal planar shape of boron trifluoride (BF3)?

VSEPR theory explains that BF3 has a trigonal planar shape because the central boron atom has three bonding pairs and no lone pairs. To minimize repulsion, these three bonding pairs arrange themselves in a plane with 120° angles between them, resulting in the trigonal planar geometry.

10. Why does sulfur hexafluoride (SF6) have an octahedral shape according to VSEPR theory?

According to VSEPR theory, SF6 has an octahedral shape because the central sulfur atom has six bonding pairs and no lone pairs. To minimize repulsion, these six bonding pairs arrange themselves at 90° angles to each other, forming an octahedral geometry with the fluorine atoms at the vertices.

11. How does VSEPR theory explain the difference in shapes between methane (CH4) and ammonia (NH3)?

VSEPR theory explains that methane (CH4) has a tetrahedral shape because it has four bonding pairs and no lone pairs around the central carbon. Ammonia (NH3) has a trigonal pyramidal shape because it has three bonding pairs and one lone pair around the central nitrogen. The lone pair in NH3 occupies more space, distorting the tetrahedral arrangement into a trigonal pyramid.

12. What is the relationship between VSEPR theory and hybridization?

VSEPR theory and hybridization are complementary concepts. VSEPR theory predicts molecular shapes based on electron pair repulsions, while hybridization explains how atomic orbitals combine to form molecular orbitals that accommodate these shapes. The predicted VSEPR geometry often corresponds to a specific hybridization state of the central atom.

13. How does VSEPR theory explain the T-shaped geometry of ClF3?

VSEPR theory explains the T-shaped geometry of ClF3 by considering that the central chlorine atom has three bonding pairs and two lone pairs. The five electron domains adopt a trigonal bipyramidal arrangement, but the presence of two lone pairs in equatorial positions results in a T-shaped molecular geometry.

14. Why does VSEPR theory predict a trigonal bipyramidal shape for PCl5 but a square pyramidal shape for BrF5?

VSEPR theory predicts a trigonal bipyramidal shape for PCl5 because it has five bonding pairs and no lone pairs around the central phosphorus atom. BrF5 has a square pyramidal shape because it has five bonding pairs and one lone pair around the central bromine atom. The lone pair in BrF5 occupies an equatorial position, distorting the trigonal bipyramidal arrangement into a square pyramid.

15. Why does VSEPR theory predict a trigonal bipyramidal shape for PCl5 but a square pyramidal shape for BrF5?

VSEPR theory predicts different shapes for PCl5 and BrF5 due to the presence of a lone pair in BrF5. PCl5 has five bonding pairs and no lone pairs, resulting in a trigonal bipyramidal shape. BrF5 has five bonding pairs and one lone pair, leading to a square pyramidal shape. The lone pair in BrF5 occupies an equatorial position, distorting the trigonal bipyramidal arrangement.

16. How does VSEPR theory account for multiple bonds in molecules like ethene (C2H4)?

VSEPR theory treats multiple bonds as a single electron domain but recognizes that they exert stronger repulsion than single bonds. In ethene (C2H4), the double bond between carbon atoms is treated as one domain, resulting in a trigonal planar geometry around each carbon atom with slightly distorted bond angles.

17. What is the limitation of VSEPR theory in predicting the shapes of larger, more complex molecules?

VSEPR theory is limited in predicting shapes of larger, complex molecules because it doesn't account for factors like steric hindrance, ring strain, or intermolecular forces. It works best for small molecules with a clear central atom and becomes less reliable as molecular complexity increases.

18. How does VSEPR theory explain the difference in bond angles between H2O (104.5°) and H2S (92.1°)?

VSEPR theory explains the difference in bond angles between H2O and H2S by considering the size of the central atom and its lone pairs. Oxygen's smaller size and more compact lone pairs lead to stronger repulsion and a wider angle in H2O. Sulfur's larger size and more diffuse lone pairs result in weaker repulsion and a smaller angle in H2S.

19. Why does VSEPR theory predict a seesaw shape for SF4?

VSEPR theory predicts a seesaw shape for SF4 because the central sulfur atom has four bonding pairs and one lone pair. The five electron domains adopt a trigonal bipyramidal arrangement, but the presence of one lone pair in an equatorial position results in a seesaw-shaped molecular geometry.

20. How does VSEPR theory explain the nonlinear structure of ozone (O3)?

VSEPR theory explains the nonlinear structure of ozone (O3) by considering that the central oxygen atom has two bonding pairs and one lone pair. These three electron domains adopt a bent geometry to minimize repulsion, resulting in a bond angle of about 116.8°, which is smaller than the ideal 120° due to the presence of the lone pair.

21. What role does electronegativity play in VSEPR theory predictions?

While VSEPR theory primarily focuses on electron pair repulsions, electronegativity differences can influence molecular geometry. Highly electronegative atoms can pull electron density away from the central atom, potentially affecting the repulsion between electron pairs and slightly modifying bond angles or molecular shapes.

22. How does VSEPR theory explain the square planar geometry of XeF4?

VSEPR theory explains the square planar geometry of XeF4 by considering that the central xenon atom has four bonding pairs and two lone pairs. The six electron domains adopt an octahedral arrangement, but the presence of two lone pairs in axial positions results in a square planar molecular geometry.

23. Why does VSEPR theory predict different shapes for BF3 and NF3?

VSEPR theory predicts different shapes for BF3 and NF3 because of the presence of a lone pair in NF3. BF3 has three bonding pairs and no lone pairs, resulting in a trigonal planar shape. NF3 has three bonding pairs and one lone pair, leading to a trigonal pyramidal shape. The lone pair in NF3 occupies more space and distorts the geometry.

24. How does VSEPR theory explain the linear shape of BeF2?

VSEPR theory explains the linear shape of BeF2 by considering that the central beryllium atom has two bonding pairs and no lone pairs. To minimize repulsion, these two bonding pairs arrange themselves 180° apart, resulting in a linear molecule with maximum separation between electron domains.

25. What is the difference between a tetrahedral and a trigonal pyramidal shape according to VSEPR theory?

According to VSEPR theory, a tetrahedral shape has four bonding pairs and no lone pairs around the central atom (e.g., CH4), resulting in perfect tetrahedral symmetry. A trigonal pyramidal shape has three bonding pairs and one lone pair (e.g., NH3), where the lone pair distorts the tetrahedral arrangement, pushing the bonding pairs closer together and creating a pyramidal structure.

26. How does VSEPR theory account for the difference in shapes between PCl5 and SF4?

VSEPR theory accounts for the difference in shapes between PCl5 and SF4 by considering the number of bonding and lone pairs. PCl5 has five bonding pairs and no lone pairs, resulting in a trigonal bipyramidal shape. SF4 has four bonding pairs and one lone pair, leading to a seesaw shape. The lone pair in SF4 occupies an equatorial position, distorting the trigonal bipyramidal arrangement.

27. Why does VSEPR theory predict a trigonal planar shape for BF3 but a trigonal pyramidal shape for PF3?

VSEPR theory predicts different shapes for BF3 and PF3 due to the presence of a lone pair in PF3. BF3 has three bonding pairs and no lone pairs, resulting in a trigonal planar shape with 120° bond angles. PF3 has three bonding pairs and one lone pair, leading to a trigonal pyramidal shape. The lone pair in PF3 occupies more space and pushes the bonding pairs closer together, distorting the planar arrangement.

28. How does VSEPR theory explain the difference in bond angles between NH3 (107°) and PH3 (93.3°)?

VSEPR theory explains the difference in bond angles between NH3 and PH3 by considering the size of the central atom and its lone pair. Nitrogen's smaller size and more compact lone pair lead to stronger repulsion and a wider angle in NH3. Phosphorus's larger size and more diffuse lone pair result in weaker repulsion and a smaller angle in PH3.

29. What is the significance of the AX notation in VSEPR theory?

The AX notation in VSEPR theory is significant because it provides a shorthand way to describe molecular geometry based on the number of bonding pairs. 'A' represents the central atom, and 'X' represents the number of bonding pairs. For example, AX2 represents a linear molecule, AX3 a trigonal planar molecule, and AX4 a tetrahedral molecule.

30. How does VSEPR theory explain the Y-shaped geometry of ClF3?

VSEPR theory explains the Y-shaped geometry of ClF3 by considering that the central chlorine atom has three bonding pairs and two lone pairs. The five electron domains adopt a trigonal bipyramidal arrangement, but the presence of two lone pairs in equatorial positions results in a Y-shaped (or T-shaped) molecular geometry.

31. Why does VSEPR theory predict a trigonal bipyramidal shape for PF5 but an octahedral shape for SF6?

VSEPR theory predicts different shapes for PF5 and SF6 based on the number of bonding pairs around the central atom. PF5 has five bonding pairs and no lone pairs, resulting in a trigonal bipyramidal shape. SF6 has six bonding pairs and no lone pairs, leading to an octahedral shape. The additional bonding pair in SF6 requires a different arrangement to minimize repulsion.

32. How does VSEPR theory explain the bent shape of SO2?

VSEPR theory explains the bent shape of SO2 by considering that the central sulfur atom has two bonding pairs and one lone pair. These three electron domains adopt a trigonal planar arrangement, but the presence of the lone pair causes the molecule to bend, resulting in a bond angle of approximately 119.5°.

33. What is the relationship between VSEPR theory and molecular polarity?

VSEPR theory is related to molecular polarity because the shape of a molecule, as predicted by VSEPR, determines whether it is polar or nonpolar. Symmetrical molecules (like BF3 or CCl4) are typically nonpolar, while asymmetrical molecules (like H2O or NH3) are often polar. The distribution of electron density, influenced by molecular geometry, affects the overall dipole moment of the molecule.

34. How does VSEPR theory account for the difference in shapes between XeF2 and XeF4?

VSEPR theory accounts for the difference in shapes between XeF2 and XeF4 by considering the number of bonding and lone pairs. XeF2 has two bonding pairs and three lone pairs, resulting in a linear shape. XeF4 has four bonding pairs and two lone pairs, leading to a square planar shape. The additional bonding pairs in XeF4 require a different arrangement to minimize repulsion.

35. Why does VSEPR theory predict a see-saw shape for SF4 but a square pyramidal shape for IF5?

VSEPR theory predicts different shapes for SF4 and IF5 due to the number of bonding and lone pairs. SF4 has four bonding pairs and one lone pair, resulting in a see-saw shape. IF5 has five bonding pairs and one lone pair, leading to a square pyramidal shape. The additional bonding pair in IF5 requires a different arrangement to minimize repulsion.

36. How does VSEPR theory explain the difference in shapes between CO2 and SO2?

VSEPR theory explains the difference in shapes between CO2 and SO2 by considering the presence of lone pairs. CO2 has two double bonds and no lone pairs, resulting in a linear shape. SO2 has two bonding pairs and one lone pair, leading to a bent shape. The lone pair in SO2 occupies more space and pushes the bonding pairs closer together, distorting the linear arrangement.

37. What is the significance of bond angles in VSEPR theory?

Bond angles are significant in VSEPR theory because they reflect the arrangement of electron domains around the central atom. They provide information about the molecular geometry and the strength of repulsion between electron pairs. Deviations from ideal bond angles can indicate the presence of lone pairs or other factors affecting molecular shape.

38. How does VSEPR theory explain the tetrahedral shape of methane (CH4)?

VSEPR theory explains the tetrahedral shape of methane (CH4) by considering that the central carbon atom has four bonding pairs and no lone pairs. To minimize repulsion, these four bonding pairs arrange themselves at 109.5° angles to each other, forming a tetrahedral geometry with the hydrogen atoms at the vertices.

39. How does VSEPR theory account for the difference in shapes between BeCl2 and H2O?

VSEPR theory accounts for the