A Guide to the Types of Van Der Waals Forces
Van Der Waals forces are the interactions between atoms and molecules that result in a pull between them. These forces consist of weak intermolecular interacting with each the nearest possible distance. The molecules do not contain any charge.
These interactions or bonds comprise of three types, such as dipole-dipole, hydrogen bonds and London dispersion forces. Their formation depends on the type of bonding between molecules.
The concept of Waals’ interactions is vast. It requires a deeper understanding of the properties and types to score better! So, go through the below pointers to get a hold of Van Der Waals interactions.
Let’s start!
Types of Van Der Waals Bonding
The Waals’s interactions depend on three types of forces, such as London forces, dipole-dipole and hydrogen bonding. They are based on the type of bonding they share within molecules or atoms. These include:
Dipole-Dipole Interactions
These bonds lead to the formation of attractive forces present in the two polar molecules having constant dipoles. These dipoles occur when atoms present close to each other contain an electronegative effect. Its occurrence results from the interaction of a molecule’s negative portion with the positive part of the other molecule.
The dipoles having opposite charges form a firm bonding among them as they attract each other with stronger forces. A molecular dipole forms when electrons share an unequal distribution within themselves.
Hydrogen chloride (HCl) is an appropriate example of Van Der Waals forces containing dipole-dipole interactions as it contains both positive and negative ends attracting others. Moreover, a molecule of HCl comprises a permanent dipole as the chlorine atom present in it is more electronegative than the hydrogen one.
London Dispersion Forces
These interactions share the weakest type of bonding among the three types of Waals forces. Their attractions arise from the short-term and induced dipoles available in most molecules and atoms. The dispersion forces are also responsible for creating dipole-induced dipole bonds.
These bonds occur when electrons available within two adjoining atoms take interim positions. They are also accountable for condensation of non-polar materials into liquids, and freezing of solid when the temperature drops. Mostly, these interactions depend on the molecules’ ability to polarize.
These weakest intermolecular forces also occur within two or more molecules when the polar ones get situated nearby. Their strength varies along with the number of electrons occurring in a molecule. Mostly, these interactions occur due to the motion of these electrons.
Hydrogen Bonding
These forces occur from a unique type of dipole-dipole interactions inside two or more hydrogen atoms. Their attractions are relatively much stronger than London dispersion forces and dipole-dipole interactions. The attractions between hydrogen bonds occur because of the strong forces between a hydrogen atom.
These atoms share a covalent type of bonding between two highly electronegative atoms, such as Oxygen, Nitrogen and Fluorine, etc. The hydrogen molecules form stronger bonds by getting attracted to O, F and N atoms, but only these atoms can form bonds with hydrogen atoms. The strength of a hydrogen bond varies between 4 kJ/mol and 50 kJ/mol.
Did you know: Interaction between water molecules is an appropriate example of Hydrogen bonding of Van Der Waals forces!
Pop Quiz 1
Solve the below question to brush up your skills!
Under what circumstances, does a real gas work closely in the ideal gas equation of Vander waal forces?
There is less pressure and higher temperature.
Both pressure and temperature are high.
Pressure appears higher, and the temperature is low.
Both pressure and temperature are low.
None of the above.
Van Der Waals Equation
While learning about the Van Der Waals forces, it is essential to know regarding its equation. The Waals equation depicts the characteristics of two real gases. It studies the excluded volume of these gases and its intensity of attraction occurring between them.
It gets elucidated as:
(P+n2aV2) (V-nb)= nRT
Where a = intensity of attraction between two or more molecules or atoms.
And b = excluded volume of real gases.
Activity: Find how molecular shape plays a vital role in impacting the strength of dispersion forces? Take expert’s guidance if necessary.
Components of Waals Interactions
The Van Der Waals forces appear as an interaction in a closely-situated position of the molecules or atoms. These forces depend on the attractions or repulsions within two or more molecules. The bonds get firmer when they occur with a short distance from 0.4 kilojoules per mole (kJ/mol) to 4 kJ/mol.
However, their pull tends to repel when situated at a distance less or within 0.4 nanometers (nm). Mostly, they appear to be highly active when they get situated at a space of less than 0.6 nanometers.
Try reading the below pointers to gain knowledge about the components of Van Der Waals bonding. They are as follows:
These bonds contain negative components that prohibit molecules from collapsing with each other. It is due to the Pauli Exclusion Principle.
The Keesom force is another key contributor to Waals interactions. There exists either repulsion or attractive interaction between dipoles, multi-poles, quadrupoles or constant charges due to the Keesom.
London dispersion force forms a vital component of the Waals bond. It arises due to the interaction between nonpolar or polar molecules.
Debye force also acts as a key contributor in the Waals forces. It is accountable for the occurrence of attractions between molecules containing an induced and permanent polarity.
Properties of Van Der Waals Bonding
Read the characteristics of Waals forces to know more of them in detail!
These interactions contain comparatively weaker, electric bonds compared to the ionic, covalent or metallic interactions.
These attractions or forces remain completely unaffected by the change in temperature apart from dipole-dipole interactions.
The attractions become addictive as it contains a huge number of molecules available with them. They are still present when the molecules get placed at a long distance.
These weak bonds are present in almost all types of materials. However, primary bonds often overpower their effects as they are relatively weaker in comparison to them.
The Waals interactions are universal, and they are accountable for the attraction of atoms or molecules within themselves.
These intermolecular bonds work with a short-range. Hence, the interactions occur when the particles get closely situated with each other. The pace of attraction is greater when the molecules or atoms get closer to each other.
Additionally, these intermolecular forces do not have the capability of saturation.
Moreover, these interactions do not possess any directional attributes.
Activity: Study the applications of these bonds in detail and try to find some suitable Van Der Waals forces examples. Take the help of your friends or teachers for additional guidance.
Interesting Facts about Waals Forces
The Waals forces are the weakest intermolecular interactions.
These bonds derive their name from a Dutch Scientist known as Johannes Diderik Van Der Waals. He found the existence of these forces while understanding the theory of a real gas in 1873.
The forces working between two dipoles are known as Keesom. It derives its name from William Hendrik Keesom.
The attraction operating between a molecule containing charge and a dipole is known as Debye. It derives its name after Peter Debye.
The Van Der Waals equation studies the properties of two gases.
The word ‘a’ in the Waals equation shows the intensity of attraction among molecules or atoms.
The firmness of a hydrogen bond varies from 4 kJ/mol to 50 kJ/mol.
Only Nitrogen, Oxygen and Fluorine atoms in a single molecule can form hydrogen bonding.
The interactions between two polarized particles are known as London forces. They derive their name after Fritz London.
Chemistry is a subject that requires in-depth knowledge of complex theories and formulas of various compounds. Therefore, you will feel the need for guidance when you get stuck with problematic areas. For easing out such problems, you can take help of our live classes and learn more engaging concepts similar to Van Der Waals forces in chemistry.
FAQs on Types of Van Der Waals Forces
1. What exactly are van der Waals forces in Chemistry?
Van der Waals forces are the collective term for the weak, short-range intermolecular forces that exist between neutral atoms and molecules. Unlike strong covalent or ionic bonds that hold atoms together within a molecule (intramolecular), these forces act between separate molecules, influencing physical properties like boiling points, melting points, and solubility.
2. What are the main types of van der Waals forces a student should know for the CBSE 2025-26 syllabus?
For the CBSE syllabus, van der Waals forces are generally categorised into three main types based on the nature of the interacting particles:
- London Dispersion Forces: These are the weakest type, present in all atoms and molecules. They arise from temporary, fluctuating electron clouds creating instantaneous dipoles.
- Dipole-Dipole Forces: These occur between polar molecules that have permanent positive and negative ends. The positive end of one molecule attracts the negative end of another.
- Dipole-Induced Dipole Forces: This interaction happens when a polar molecule with a permanent dipole induces a temporary dipole in a nearby non-polar molecule, leading to a weak attraction.
3. What is the difference between a van der Waals force and a covalent bond?
The primary difference lies in their nature, strength, and the particles they act between. A covalent bond is a strong intramolecular force involving the sharing of electrons between atoms within a single molecule. In contrast, a van der Waals force is a much weaker intermolecular force that acts between different, separate molecules due to temporary or permanent charge fluctuations.
4. Can you provide some real-world examples where van der Waals forces are important?
Van der Waals forces, despite being weak, have significant real-world applications and effects. For example:
- Geckos Climbing Walls: Geckos can stick to surfaces due to the cumulative effect of millions of tiny hairs on their feet, which create strong London dispersion forces with the wall's surface.
- Liquefaction of Gases: Non-polar gases like nitrogen (N₂) and helium (He) can be turned into liquids because van der Waals forces cause attraction between the gas molecules at low temperatures and high pressures.
- Structure of Graphite: The layers of carbon atoms in graphite are held together by weak van der Waals forces, allowing them to slide over each other, which is why graphite is used as a lubricant and in pencils.
5. How does the shape of a molecule influence the strength of London dispersion forces?
The shape of a molecule has a direct impact on the strength of its London dispersion forces. Molecules with a larger, more spread-out surface area can have more points of contact with neighbouring molecules. For instance, a long, chain-like molecule like n-pentane has a larger surface area and thus stronger dispersion forces than a compact, spherical molecule like neopentane, even though both have the same chemical formula (C₅H₁₂). This is why n-pentane has a higher boiling point.
6. Is hydrogen bonding considered a type of van der Waals force?
This is a common point of confusion. A hydrogen bond is a special, exceptionally strong type of dipole-dipole interaction. While it technically falls under the general category of intermolecular forces, its strength (typically 10-40 kJ/mol) is significantly greater than other van der Waals forces. Due to this unique strength and its specific requirement (a hydrogen atom bonded to a highly electronegative atom like N, O, or F), it is often treated as a distinct class of intermolecular bond.
7. Why do van der Waals forces only work over very short distances?
Van der Waals forces are highly dependent on distance because they originate from the interactions of electron clouds and dipoles. The strength of these forces decreases rapidly as the distance between molecules increases, typically following an inverse power law (like 1/r⁶). At larger distances, the charge fluctuations or permanent dipoles are too far apart to have a significant attractive effect. Conversely, if molecules get too close, their electron clouds begin to repel each other, overpowering the weak attraction.
8. What is the difference between Keesom, Debye, and London forces?
These three terms represent a more detailed breakdown of the components that make up the overall van der Waals interactions:
- Keesom Force: This is the interaction between two permanent dipoles (as seen in polar molecules like HCl).
- Debye Force: This describes the interaction between a permanent dipole and an induced dipole that it creates in a neighbouring non-polar molecule.
- London Force: This is the interaction between two temporary, instantaneously induced dipoles, which occurs in all molecules.
