What causes dispersion forces? What factors determine the strengths of dispersion forces between

step 1 This question is asking about a description of dispassion forces. Now when you are looking at di

What causes dispersion forces? What factors determine the...

Key Concepts

Molecular Size and Shape

The size and shape of molecules play a significant role in determining the strength of dispersion forces. Larger, more elongated molecules generally have more electrons and a greater surface area for interaction, which contributes to stronger dispersion forces. Additionally, the geometry can influence how closely molecules can approach each other, affecting the overall strength of these forces.

London Dispersion Forces

London dispersion forces are a type of van der Waals force that arise due to temporary fluctuations in electron density within molecules or atoms. Even in nonpolar substances, these momentary imbalances can create temporary dipoles that induce complementary dipoles in neighboring particles, leading to an attractive force between them.

Instantaneous and Induced Dipoles

These dipoles are central to the existence of dispersion forces. An instantaneous dipole occurs when the electron distribution in an atom or molecule momentarily favors one side, and this instantaneous dipole can induce a dipole in a nearby atom or molecule, resulting in an attractive interaction.

Polarizability

Polarizability refers to how easily the electron cloud of an atom or molecule can be distorted by an electric field. Higher polarizability means that the electron cloud is more easily displaced, enhancing the magnitude of instantaneous dipoles and consequently increasing the strength of dispersion forces.

Transcript

00:01 This question is asking about a description of dispassion forces.

00:09 Now when you are looking at dispassion forces, these are weak intermolecular forces of attraction that arise from temporary dipoles within molecules.

00:20 So the main key concepts here about dispassion forces, they are weak and they are also intermolecular forces.

00:30 Unlike intramolecular forces like covalent bones these ones are intermolecular forces they exist between molecules not between not within a certain molecule these are not bones that arise from atoms these are more like attractions between molecules so they are weak and they are also intermolecular and they arise is as a result of temporary dipoles.

01:09 So what happens is, let's say we've got a molecule.

01:16 We know that molecules are made from atoms and atoms are made from electrons.

01:23 So what we need to appreciate is that these electrons are always in motion.

01:31 That is constant and random motion.

01:38 So what happens is when these electrons are moving around, these electrons are moving around.

01:47 At times what happens is when they move to the edge of the molecule, they tend to attract the positive part or the nucleus of the other molecule or the other atoms in another molecule.

02:02 So what happens is you've got a temporary negative charge where the electrons are concentrated and at the same time since positive and negative attract, you've got a temporary positive charge in another molecule...

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