London dispersion force

London Dispersion Force

The London Dispersion Force, also known as the dispersion force, London forces, or instantaneous dipole-induced dipole forces, is a type of intermolecular force that exists between all atoms and molecules. It is named after the German-American physicist Fritz London, who first described this phenomenon in 1930.

Overview

The London Dispersion Force is a weak intermolecular force that arises due to temporary fluctuations in electron distribution within atoms or molecules. These fluctuations create temporary dipoles, which induce similar dipoles in neighboring atoms or molecules. These induced dipoles then attract each other, resulting in a net attractive force between the particles.

Mechanism

The London Dispersion Force is a result of the quantum mechanical nature of electrons. According to quantum mechanics, electrons are not always evenly distributed around an atom or molecule. At any given moment, there can be a temporary imbalance in electron distribution, leading to the formation of a temporary dipole. This dipole induces a dipole in a neighboring atom or molecule, resulting in an attractive force between them.

Strength

The strength of the London Dispersion Force depends on several factors, including the number of electrons in the atom or molecule and the shape of the molecule. Generally, larger atoms or molecules with more electrons have stronger London Dispersion Forces. Additionally, molecules with a larger surface area or more branching tend to have stronger London Dispersion Forces.

Importance

The London Dispersion Force is the weakest of all intermolecular forces. However, it plays a crucial role in determining the physical properties of substances. It is responsible for the condensation of nonpolar gases into liquids and the solidification of nonpolar substances. It also affects the boiling points, melting points, and viscosity of substances.

Examples

The London Dispersion Force is present in all atoms and molecules, regardless of their polarity. However, it is particularly important in nonpolar molecules. For example, noble gases such as helium, neon, and argon exhibit only London Dispersion Forces since they consist of individual atoms. Similarly, nonpolar molecules like methane (CH4) and carbon dioxide (CO2) rely primarily on London Dispersion Forces for intermolecular attraction.

Conclusion

In conclusion, the London Dispersion Force is a weak intermolecular force that arises due to temporary fluctuations in electron distribution. It is present in all atoms and molecules, playing a crucial role in determining their physical properties. While it is the weakest intermolecular force, it is essential for understanding the behavior of nonpolar substances. Further research and understanding of the London Dispersion Force continue to contribute to various fields, including chemistry and materials science.

See Also

• Intermolecular Forces
• Van der Waals Forces
• Hydrogen Bonding

References

1. London, F. (1930). The general theory of molecular forces. Transactions of the Faraday Society, 26, 393-410. 2. Atkins, P., & de Paula, J. (2010). Atkins' Physical Chemistry. Oxford University Press.