[Chemistry Class Notes] on Types of Van Der Waals Forces Pdf for Exam

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!

1. Under what circumstances, does a real gas work closely in the ideal gas equation of Vander waal forces?

1. There is less pressure and higher temperature.

2. Both pressure and temperature are high.

3. Pressure appears higher, and the temperature is low.

4. Both pressure and temperature are low.

5. 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:

• 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.

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 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.

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

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.