A Model To Explain London Dispersion Forces

# A Model To Explain London Dispersion Forces - • It is...

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A Model To Explain London Dispersion Forces: Helium atoms (2 electrons) Consider the particle nature of electrons The average distribution of electrons around each nucleus is spherically symmetrical The atoms are non-polar and posses no dipole moment The distribution of electrons around an individual atom , at a given instant in time , may not be perfectly symmetrical o Both electrons may be on one side of the nucleus o The atom would have an apparent dipole moment at that instant in time (i.e. a transient dipole) o A close neighboring atom would be influenced by this apparent dipole - the electrons of the neighboring atom would move away from the negative region of the dipole Due to electron repulsion, a temporary dipole on one atom can induce a similar dipole on a neighboring atom This will cause the neighboring atoms to be attracted to one another This is called the London dispersion force (or just dispersion force)

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Unformatted text preview: • It is significant only when the atoms are close together The ease with which an external electric field can induce a dipole (alter the electron distribution) with a molecule is referred to as the "polarizability" of that molecule • The greater the polarizability of a molecule the easier it is to induce a momentary dipole and the stronger the dispersion forces • Larger molecules tend to have greater polarizability o Their electrons are further away from the nucleus (any asymmetric distribution produces a larger dipole due to larger charge separation) o The number of electrons is greater (higher probability of asymmetric distribution) thus, dispersion forces tend to increase with increasing molecular mass • Dispersion forces are also present between polar/non-polar and polar/polar molecules (i.e. between all molecules) •...
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A Model To Explain London Dispersion Forces - • It is...

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