On the valence electrons depends on their distance from the nucleus and on theĬore charge. So valenceĮlectrons make the greatest contribution to the polarizability. The electrons which are the most easily displaced in an atom or moleculeĪre the valence electrons, these are the furthest from the nucleus. Of the instantaneous dipole can be large with the result producing a strongerĪttraction between particles. When the polarizability is large for a particular atom or molecule the magnitude On polarizability are the units of volume, m 3. With many electrons, the polarizability of the substance is large. The electrons occupy a large volume of space, which occurs in an atom or molecule The electrons and nuclei can be displaced from their average positions. Polarizability of an atom or a molecule is a measure of the ease with which Nonpolar molecules is inversely proportional to the seventh power of the distanceĪnd directly proportional to a property of each molecule called polarizability. It has been shown (not in class) that the force of attraction between two In all molecules whether they are polar or nonpolar. So the magnitude of the dispersionįorces increases with increasing molecular size. The easier the electron cloud can be polarized. The larger the molecule the further the electrons are from the nucleus and The electron cloud is distorted or polarized. The strength of the London dispersion forces depends on how easily When this occurs, even for an instant there is a small attraction between the Another atom near this instantaneous dipole will also be effected causingĪ shift of its electron distribution resulting in a small dipole around it. Which gives rise to an instantaneous dipole. The nuclei, when this occurs there is a very small charge separation created ![]() ![]() Once and a while we observe that the electrons are unequally distributed around Later would reveal a return to an equal distribution of the electrons. However, occasionally we see,īut not very often, an unequal sharing of the electrons. Symmetric distribution of the electron density. If we take "snapshots" of the electron distribution we would generally see a In class we saw an animation of a collection of monoatomic neutral atoms. These compounds do not have permanent dipoles as occur in heteronuclearĭiatomic molecules (HCl, HBr, HI, etc) and polar compounds (SO 2, ![]() Monoatomic atoms (noble gases), diatomicĪnd nonpolar compounds (CH 4, CCl 4, BF 3, BeH 2,Įtc.) are all characterized by a symmetric sharing of electrons in the atom Untitled Document Chapter12: Dispersion Forces and Hydrogen Bonding London dispersion forces occur between atoms
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