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Dipole Induced Dipole Forces

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Definition of Dipole Induced Dipole Forces

Induced dipole forces result when an ion or a dipole induces a dipole in an atom or a molecule with no dipole. These are weak forces

More About Dipole Induced Dipole Forces

  • An ion-induced dipole attraction is a weak attraction that results when the approach of an ion induces a dipole in an atom or in a nonpolar molecule by disturbing the arrangement of electrons in the nonpolar species
  • A dipole-induced dipole attraction is a weak attraction that results when a polar molecule induces a dipole in an atom or in a nonpolar molecule by disturbing the arrangement of electrons in the nonpolar species
  • This type of attractive forces operate between the polar molecules having permanent dipole and the molecules lacking permanent dipole
  • Permanent dipole of the polar molecule induces dipole on the electrically neutral molecule by deforming its electronic cloud
  • Thus an induced dipole is developed in the other molecule
  • In this case interaction energy is proportional to 1/ r 6 where ‘r’ is the distance between the two molecules
  • Induced dipole moment depends upon the dipole moment present in the permanent dipole and the polarisability of the electrically neutral molecule
  • Molecules of larger size can be easily polarized
  • High polarisability increases the strength of attractive interactions
  • In this case also cumulative effect of dispersion forces and dipole-induced dipole interactions exists
  • They are weak compared to the Intramolecular forces, the forces which keep a molecule together
  • For example, the covalent bond present within HCl molecules is much stronger than the forces present between the neighboring molecules, which exist when the molecules are sufficiently close to each other
  • The induced dipole forces appear from the induction which is the attractive interaction between a permanent multipole on one molecule with an induced multipole on another
  • One example of an induction-interaction between permanent dipole and induced dipole is the interaction between HCl and Ar

Question:

An atom or molecule can be temporarily polarized by a nearby species. Polarization separates centers of charge giving

    A. permanent dipole
    B. temporary charges
    C. Induced ions
    D. radicals

Answer: C - Induced dipoles are responsible for the London dispersion forces. The heavier the molecule, the larger the induced dipole will be. Thus, London dispersion forces are strong for heavy molecules.