Van der Waals force

In chemistry, the term Van der Waals force originally referred to all forms of intermolecular forces; however, in modern usage it tends to refer to intermolecular forces that deal with forces due to the polarization of molecules. Forces that deal with fixed or angle averaged dipoles (Keesom forces) and free or rotation dipoles (Debye forces) as well as shifts in electron cloud distribution (London Forces) are named after the Dutch chemist Johannes Diderik van der Waals who first documented these interactions.

Related Topics:
Chemistry - Intermolecular force - Keesom forces - Debye forces - London Forces - Johannes Diderik van der Waals

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Van der Waals interactions are observed in noble gases, which are very stable and tend not to interact. This is why it is difficult to condense them into liquids. However, the larger the atom of the noble gas (the more electrons it has), the easier it is to condense the gas into a liquid. This happens because when the electron cloud surrounding the gas atom gets large, it does not form a perfect sphere around the nucleus. Rather, it's only spherical if averaged over longer times and generally forms an oval, which has a slight negative charge on one side and a slight positive charge on the other. The atom becomes a temporary dipole. This induces the same shift in neighboring atoms and spreads from one atom to the next. Unlike charges attract and the induced dipoles are held together by dispersion force (or Van der Waals force).

Related Topics:
Noble gases - Condense - Liquid - Atom - Electron cloud - Nucleus - Oval

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The Van der Waals force is the force to which the gecko's climbing ability is attributed. A gecko can hang on a glass surface using only one toe. Efforts continue to create a synthetic "gecko tape" that exploits this knowledge. So far research has produced some promising results - early research yielded an adhesive tape product, which only obtains a fraction of the forces measured from the natural material, and new research has yielded a discovery that purports 200 times the adhesive forces of the natural material.

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