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This is on the outer edge of the molecules, making them closest to the aether or empty space of the spatial layer.
This is why they are the weakest of the intermolecular forces.
This is called London dispersion forces by Physics.
These exist between all molecules, regardless of polarity.
These forces arise from the interaction between the space particles and the aetherspace.
At any given moment, the intra-atherspace may be arranged in different ways that will cause a void in the intra-aetherspace that then causes an attraction facilitated by space particles.
The attraction lasts only as long as the void exist.
Key Characteristics
- Strength: Weakest of all intermolecular forces (0.05–40 kJ/mol)
- Range: Very short (acts only over small distances)
- Present in: All molecules (polar and nonpolar)
- Temperature dependence: Decreases with increasing temperature as the temperature removes voids by agitation
Factors Affecting Strength:
| Factor | Effect | Example |
|---|---|---|
| Molar mass | Higher mass → stronger forces | I₂ (solid) vs. F₂ (gas) |
| Number of electrons | More electrons → stronger forces | Xe (gas) vs. He (gas) |
| Molecular shape | More surface area → stronger forces | n-pentane (liquid) vs. neopentane (gas) |
Examples
| Substance | Formula | State at 25°C | Reason |
|---|---|---|---|
| Helium | He | Gas | Very low mass, few electrons |
| Neon | Ne | Gas | Low mass, few electrons |
| Argon | Ar | Gas | Moderate mass |
| Krypton | Kr | Gas | Higher mass |
| Xenon | Xe | Gas (near liquid) | High mass, stronger dispersion |
| Iodine | I₂ | Solid | Very high mass, strong dispersion |
Real-World Importance
- Nonpolar liquids: Gasoline and oil are liquids at room temperature primarily due to dispersion forces.
- Noble gas liquefaction: Dispersion forces allow noble gases to be liquefied at low temperatures.
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