awangsetyawan: April 2012

Van der Waals forces in chemistry refers to certain types of inter-molecular forces. This term originally referred to any type of force between molecules, and is still sometimes used in that sense, but today more commonly refers to the forces arising from the polarization of molecules into dipoles.
This includes the force arising from permanent dipoles (Keesom forces), dipole rotation or free (Debye forces) as well as the shift of the electron cloud distribution (London style).
Van der Waals forces: drag force between atoms or molecules, this force is much weaker than the forces that arise due to the bond valence and magnitude is 10-7 times the distance between atoms or molecules. This style is causing nonideal nature of the gas and cause the lattice energy of molecular crystals. There are three things that cause this style:

    Dipole-dipole interaction, ie elektrostatistik attraction between two molecules with permanent dipole moment.
    Imbasan dipole interaction, that occurs due to dipole polarization by neighboring molecules.
    Dispersion forces arising from the dipole is small and in the blink of an atom.

The origin of van der Waals dispersion forces
Dipole-dipole swings while
Attractions are there in nature is electric. At the symmetric molecules such as hydrogen, however, does not look distorted to produce the electrically positive or negative parts. But only in average shape.
The diagram in the form of an oval (the lozenge-shaped) describe a small molecule that is symmetrical - H2, perhaps, or Br2. Shading indicates no sign of electrical distortion.
However, the electron continues to move, immediately and at one time the electron may be found at the end of the molecule, forming the tip -. On the other end while the shortage of elaktron and a +.Note: (pronounced "delta") means "little" (slightly) - so + means "slightly positive".
The electrons can move to the other end, reverse the polarity of the molecule.
"Sloshing around" a constant of the electron in the molecule causes rapid fluctuations in the molecular dipoles of the most symmetrical. This occurs in monatomic molecules - molecules of noble gases, such as helium, which consists of a single atom.
If the two helium electrons are on one side simultaneously, the core is not protected by the electron as it should for the moment.
Temporary dipoles that how the membemberikan increase intermolecular dayaarik
Imagine a molecule that has a polarity which is approached by a temporary one that happens to include non-polar just at that moment. (Events that are not favored, but this makes the diagram more easily described! In fact, a single molecule is likely to have a greater polarity than the other at that time - and will therefore be the dominant one).
Like molecule found on the right, electrons will tend to be drawn by the slightly positive on the left.
This results in the receipt of the molecular induced dipole, oriented in a manner which is pulled towards the + end end - the other.
At the electrons on the left side of the molecule can move up the other end. In doing this, they will repel the electrons on the right hand one.
Reverses the polarity of both molecules, but you are still interested in a + -. During the molecules close to each other polarity will continue to fluctuate in synchronization so that the attraction is always maintained.
There is no reason why this should be limited to two molecules. Molecules close to each other during movement of the electrons are aligned molecules can occur in a number very much.
This diagram shows how the overall defects of molecules bonded together in a solid by using the van der Waals force. In the latter condition, of course, you will describe a slightly different arrangement of electrons as they change - but stay in tune

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