What is a dipole (chemistry)?


Hi I really don’t understand this part. It isn’t in my Grade 9 syllabus but alot of points in my notes touch on dipole in atoms. Can someone explain it to me using analogies or just simple words?

For example, heres an extract from my notes:

1. Most ionic compounds are soluble due to favourable ion-dipole interactions
1. water separates positive ions from negative ions, causing them to dissolve

In: Chemistry

Every atom in a molecule has an electronegativity. The electrons between two atoms are nearer to the atom with the higher electronegativity. If every electron in a molecule go in the same direction, there are two magnetic poles, because of the negative charge of them. Thats a dipole. I wouldn’t be a dipole if as example the electrons all go to one atom. (Sorry for bad english)

Water molecules are polar because of their physical shape. The two hydrogen atoms and single oxygen form a V shape, as they share elections. The hydrogen atoms are ‘lending’ their elections to the oxygen. The result is that the water molecule at the ‘top’ of the V is more positively charged than the bottom, creating a dipole.

Compare this with a non-polar methane molecule, CH4. Here the hydrogen atoms are evenly distributed around the carbon atom, so there is no charge difference.

Think of a dipole like two magnets, but one is stronger than the other. There’s a tiny, negative ball in between those two magnets and both magnets want the ball. However, only one can have it and the one with the stronger magnetic pull gets the ball momentarily, mostly, or permanently.

Dipole interactions such as London dispersion forces (also called dipole-induced dipole interactions) make one magnet get the ball momentarily. These are the weakest kind of dipole interactions.

Dipole-dipole is the general case for two polar molecules interacting with each other. This means that one magnet gets the ball most of the time and creates tiny positive and negative charges on the molecule that let it interact with all the others in the substance or solution.

Hydrogen bonding is much like the dipole-dipole case, but the interaction created between the molecules is stronger. This interaction happens when you have an N, O, or F bonded to a hydrogen.

Ion dipole is the strongest intermolecular force. This is when you dump an ionic substance into a solvent (preferably something polar, like water) that will break up when it dissolves. This break-up is when one magnet permanently takes the ball. The ions created then interact with the solvent.

Here’s a [super cool chart I found about intermolecular forces](https://imgur.com/a/IsZC2iX). This lists out some of the ones I talked about and listed the energy contained in the interactions indicating how strong they are.

Edit: if you want learn more, [here’s a khan academy video on intermolecular forces](https://youtu.be/pBZ-RiT5nEE). They may be called van der Waals forces, but they’re the same thing. Biology tends to use the latter name.