An electric dipole consists of 2 oppositely charged particles (having the same magnitude) separated over a small distance. Now if opposite charges attract each other then wouldn't 2 charges making a dipole eventually collide with each other and would just stick to each other?

If yes, then how do dipoles exist in reality? I know that polar molecules consist of dipoles but what prevents such charges to stick with each other?


In polar molecules specifically, consider the structure of the atoms making up the molecule. Using H2O as an example, as PhysicsDave said, the electrons of the hydrogen atoms exist in a low-energy, stable configuration in which they are around the oxygen atom more often, which results in the oxygen atom having higher electron density and being more negatively charged in comparison to the more positively charged hydrogens.

Though this dipole moment exists within the molecule, it does not bring the atoms out of their current configuration. Hydrogen and oxygen atoms cannot get any closer because their nuclei (both positively charged) would repel each other and increase the energy of the system. And the electrons cannot collide with the nuclei (at normal, low energy environments) because electrons are bound in specific, quantized orbitals around the nuclei and can only exist in those discrete states (which is why negative electrons can orbit positive nuclei without spiraling into them). The attraction between opposite charges definitely exists, but no, the particles will not collide because of it.


Consider H20, a water molecule, before reaction we have neutral H atoms and neutral O atoms (actually neutral H2 and O2 molecules). After reaction 2 H attach to the O, the H electrons find a very low energy configuration (bond) where they spend most of their time closer to the O than the H, thus on a small scale we tend to see a positive end and negative end in the molecule. (The 2 Hs attach at an angle, its not symmetric.) If we look from a distance we still see a neutral molecule, but it is only when we get really close to the molecule that we see the dipole action and since other water molecules are also very small they can interact, hence water is polar and great at dissolving other polar molecules.

  • $\begingroup$ but what prevents opposite charges in a dipole to essentially not stick with each other(because opposite charges attract right?) $\endgroup$ Apr 29 '19 at 13:59
  • $\begingroup$ 2 water molecules can stick together nicely. $\endgroup$ Apr 29 '19 at 14:22
  • $\begingroup$ @PhysicsDave "2 water molecules can stick together nicely" If that's the case, then I'd say that O and H within a water molecule "stick" better than 2 water molecules $\endgroup$
    – Eagle
    Apr 29 '19 at 14:30
  • $\begingroup$ Your first comment is completely wrong. Strong force does not do what you say. Read wiki and Is there strong interaction between electrons? $\endgroup$
    – Eagle
    Apr 29 '19 at 14:39
  • $\begingroup$ the positives are in the nuclei (protons) and the negatives are the electrons. The electrons want to go to the nucleus but can not because their velocity increases so much that their position becomes uncertain (Heisenberg), this is a complex concept of Quantum Mechanics. (Before Quantum Mechanics scientists said there was a force that kept the electrons out.) The molecule is polar as the O protons (8 of them) pull all the electrons close and the H side looks more positive and the O side looks more negative. $\endgroup$ Apr 29 '19 at 15:43

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