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Encyclopedia > Van der Waals radius

The van der Waals radius of an atom is the radius of an imaginary hard sphere which can be used to model the atom for many purposes. Van der Waals radii are determined from measurements of atomic spacing between pairs of unbonded atoms in crystals. Properties For alternative meanings see atom (disambiguation). ... A sphere is, roughly speaking, a ball-shaped object. ... Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ...

The van der Waals radius is named after Johannes Diderik van der Waals, winner of the 1910 Nobel Prize in Physics. van der Waals Johannes Diderik van der Waals (November 23, 1837 – March 8, 1923) was a Dutch scientist famous for his work on the equation of state for gases and liquids, for which he won the Nobel Prize in physics in 1910. ... 1910 in topic: Arts Architecture- Art- Film- Literature- Music- Television Science and technology Aviation- Rail transport- Science Other topics Australia- Canada- Ireland- South Africa- Sport Births- Deaths Lists of leaders: State leaders - Religious leaders 1910 was a common year starting on Saturday (see link for calendar). ... List of Nobel Prize laureates in Physics from 1901 to the present day. ...

Real gases do not behave exactly as predicted. In some cases the deviation can be extremely large. For example, ideal gases could never become liquids or solids, no matter how much they were cooled or compressed. Modifications of the ideal gas law, PV = RT, were therefore proposed. Particularly useful and well known is the van der Waals equation of state: (P + a/V2) (V - b) = RT, where a and b are adjustable parameters determined from experimental measurements carried out on actual gases. Their values vary from gas to gas. A gas is one of the phases of matter. ... A liquid will assume the shape of its container. ... A solid is a state of matter, characterized by a definite volume and a definite shape (i. ... The ideal gas law or equation is the equation of state of an ideal gas. ... The ideal gas law or equation is the equation of state of an ideal gas. ... The title given to this article is incorrect due to technical limitations. ...

The van der Waals equation also has a microscopic interpretation. Molecules interact with one another. The interaction is strongly repulsive in close proximity, becomes mildly attractive at intermediate range, and vanishes at long distance. The ideal gas law must be corrected when attractive and repulsive forces are considered. For example, the mutual repulsion between molecules has the effect of excluding neighbours from a certain amount of territory around each molecule. Thus, a fraction of the total space becomes unavailable to each molecule as it executes random motion. In the equation of state, this volume of exclusion (b) should be subtracted from the volume of the container (V), thus: (V - b). The other term that is introduced in the van der Waals equation, a/V2, describes a weak attractive force among molecules, which increases as V decreases and molecules become more crowded together.

Related articles

The title given to this article is incorrect due to technical limitations. ... 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. ...

External links

  • Structural Biology Glossary: van der Waals radii
  • Real Gases and the van der Waals Equation



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