Intermolecular forces are forces of attraction between molecules. These forces influence properties of substances such as boiling and melting points, phases at room temperature, viscosity and many more.
Intermolecular forces can be divided into 4 major categories:
This is the strongest intermolecular force. It is present in all ionic compounds. To recognize it, look at the formula and see if it has metal with a nonmetal, or metal with polyatomic ion.
2. HYDROGEN BONDING
Even though there is a word bonding in its name, it is still a force and not a bond. Hydrogen bonding is present in molecules that have OH, NH or FH. It is the strongest type of dipole-dipole force, and is usually written separately.
This type of force is present in polar molecules.
4. DISPERSION (also known as Van Der Waals Forces)
This type of force is present in all substances. However, nonpolar molecules have ONLY dispersion force while others have dispersion force and other forces.
It is also important to note that dispersion force is the weakest force. The strength of dispersion forces is connected to the molar mass. The higher the molar mass, the stronger the dispersion force will be.
For example: H2 should have weaker dispersion forces than Cl2 since it has lower molar mass.
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