Intramolecular Forces
Intramolecular forces act within a molecule and are responsible for holding the molecule together through covalent or ionic bonds.
Intermolecular Forces
Intermolecular forces, on the other hand, are attractive or repulsive forces that act between molecules in a substance and affect interactions between molecules. These forces are classified into the following types: hydrogen bonds, London dispersion forces, and Van der Waals forces.
Hydrogen Bonds
Hydrogen bonds are a type of intermolecular force that involves the attraction between a hydrogen atom bonded to an electronegative atom and an electronegative atom of a different molecule. This bond can also occur between different regions of the same large molecule.
Hydrogen Bonding and Properties Example
An example of hydrogen bonding is observed in water molecules, where strong hydrogen bonding between hydrogen and oxygen results in relatively high melting and boiling points, high surface tension, and viscosity. As a result, water can dissolve many ionic and polar covalent substances. In contrast, ethane molecules do not exhibit hydrogen bonding, leading to low melting and boiling points, low surface tension, and viscosity. In this case, ethane can only dissolve nonpolar covalent substances.
Van der Waals Forces
Van der Waals forces are another type of intermolecular force that result from attractive or repulsive forces due to a random, short-lived redistribution of electrons. These forces can be categorized as dipole-dipole interactions, dipole-induced dipole interactions, and London dispersion forces.
London Dispersion Forces
London dispersion forces are a type of Van der Waals force that occur due to temporary attractive force resulting from the formation of temporary (instantaneous) dipoles when the electrons in two adjacent atoms occupy positions that induce charge redistribution. These forces are the weakest intermolecular force and mostly affect nonpolar substances, with the strength increasing with the molecular weight of the compound. They are responsible for determining the physical state of nonpolar substances, as demonstrated by gecko feet sticking to glass and other smooth surfaces.
In summary, intramolecular forces act within a molecule through covalent or ionic bonds, while intermolecular forces act between molecules and are classified into types such as hydrogen bonds, Van der Waals forces, and London dispersion forces. Each type of intermolecular force has specific properties and examples, demonstrating its impact on the physical and chemical properties of substances.
