London Dispersion Definition
Εισαγωγή:
London Dispersion refers to a type of intermolecular force that exists between atoms or molecules. Named after Fritz London, who first proposed its existence in 1930, London Dispersion is also known as dispersion forces or instantaneously induced dipole-induced dipole forces. It is one of the weakest intermolecular forces but plays a crucial role in various physical and chemical phenomena.
Ορισμός:
London Dispersion forces arise due to temporary fluctuations in electron distribution within atoms or molecules. These fluctuations result in the temporary formation of instantaneous dipoles. When these temporary dipoles occur, neighboring atoms or molecules can induce a dipole in one another, leading to a weak attractive force between them. This attractive force is known as London Dispersion force.
This force is caused by the constantly changing electron cloud distributions. At any given moment, there could be a slightly higher electron density in one region of an atom or molecule, creating a temporary dipole. This dipole can then induce a dipole in a neighboring atom or molecule, leading to an attraction between them.
Factors influencing London Dispersion forces:
– Number of electrons: The larger the number of electrons in a molecule, the greater the chances of temporary fluctuations in electron distribution. Therefore, molecules with more electrons tend to have stronger London Dispersion forces.
– Molecular shape: London Dispersion forces also depend on the shape of the molecule. Generally, molecules with larger surface areas have stronger dispersion forces since there are more opportunities for temporary dipoles to form.
Examples of London Dispersion forces:
– Noble gases: The noble gases (such as helium, neon, argon, etc.) are monatomic elements with weak intermolecular forces. The only intermolecular force that exists between noble gas atoms is London Dispersion forces.
– Hydrocarbons: Organic compounds consisting of carbon and hydrogen atoms, like methane or butane, have London Dispersion forces as the primary intermolecular force.
– Halogens: Halogen molecules, such as chlorine or bromine, have London Dispersion as the dominant intermolecular force.
Importance in physical and chemical phenomena:
– Boiling and melting points: London Dispersion forces contribute to the boiling and melting points of substances. Generally, substances with stronger dispersion forces have higher boiling and melting points.
– Solubility: London Dispersion forces also play a role in solubility. Nonpolar substances tend to dissolve in nonpolar solvents because London Dispersion forces can form between the solute and solvent molecules.
– Viscosity: The viscosity of a substance can be influenced by London Dispersion forces. Generally, substances with stronger dispersion forces have higher viscosities.
συμπέρασμα:
Συμπερασματικά, London Dispersion forces are weak intermolecular forces that arise due to temporary fluctuations in electron distribution. Despite being weak, they are omnipresent and play a crucial role in various physical and chemical phenomena. Understanding London Dispersion forces is essential for comprehending intermolecular interactions and their impact on the properties of substances.
