Van der Waals question

How is the temporary dipole created? Some websites say that it is due to the random movement of electrons creating a dipole, but then some people say that its due to two atoms coming close to each other. However, if it was due to the electrons randomly moving wouldnt there always be some sort of switching dipole, so why do some people say that when the atom is on its own there is no longer a dipole???

Also, how is it possible that van der waals forces act on all molecules? Eg how can they act between molecules that all have permanent dipoles?

(edited 5 years ago)

Reply 1

virtualcounselor

from what I was told / taught, I think temporary dipoles are usually formed when you have elements with similar electronegativities (so they have an equal distribution of electrons) whereas permanent dipoles are formed when you have elements with a great difference in electronegativity - so they have different electronegativities and the atom with the greatest electronegativity takes the lone pair of electrons

(edited 5 years ago)

Reply 2

michaela0899

You get van der waala because of the imbalance of electrons due to their movement. Think of it as if there are more electrons on one side than the other therefore that side will be more negative. This negativity will repel the electrons in a neighbouring atom and will be attracted to the positivity it creates in that atom so they will move closer to each other. All have vander waals because electrons are constantly moving in all the atoms