Major Intermolecular Forces

Intermolecular

forces

are the

forces

between particular molecules, we are talking about the forces of attraction. The forces of attraction between molecules are really what end up governing all physical properties and when I say physical properties I mean boiling point, melting point, viscosity, surface tension, things like that. our physical properties and is really governed by the strength with which these molecules are bonded together. It turns out that many of these

intermolecular

forces also affect how chemicals react because many of these same forces govern how chemicals come together and then whether you can bring them together. You have the possibility of a chemical reaction, we generally cover three basic

intermolecular

forces that we give three different names to, the differences are quite subtle, it all comes down to the difference between a positive charge and a negative charge, that's really what chemical reaction is all about. pull. so you have positive and you have negative the more positive it is, the more negative it is, the stronger the force.

This is simply a cool Amba cat rack. Positive sin attracts negative and we have all degrees of this. It's just a question of how positive and how negative. Most molecules that are neutral species do not have completely positive and completely negative, which tends to be the world of ionic molecules, which is why we constantly write partial positive and partial negative, we even have the way we symbolize it in the paper, what should be used. In fact, if you can get enough of a distribution within your molecule where you have a lot of positive charge on one side and a negative charge on the other, you can get what we call a polar molecule, a permanent one.

The dipole is a polar molecule and if you have a permanent dipole you will have a configuration within the molecule where you will always have a partial positive, you will always have a partial negative and those will join together, that is called dipole dipole winter action and that is the most strong that can be had within a molecule with another molecule. Now we have a subset of that that is actually the stronger version, even stronger than a normal dipole-dipole and we call it a hydrogen bond and it's actually because it involves hydrogen being the partial positive part of this molecule every Once hydrogen is covalently bonded to a very electronegative element and I'll be specific here, it has to be bonded to fluorine, oxygen or nitrogen and when it is it becomes partially positive and the oxygen, nitrogen or fluorine becomes so partially negative that you get an even greater amount of attraction, so we go ahead and classify that in its own class, we call it hydrogen bonding, but it's really just dipole-dipole interaction, just one level higher on the lower end of the scale, They are non-polar. molecules are now non-polar molecules that do not have any dipole moment, they are usually non-polar due to symmetry arguments, meaning that whatever you argue pointing in one direction there is the opposite wave covered somewhere else in the molecule, so all the symmetry erases the polarity of the molecule.

An example of this is carbon tetrachloride. Carbon tetrachloride has four very polar carbon-chlorine bonds, but they all cancel each other out in charge distribution, making it a non-polar molecule; however, it will attract another molecule of carbon tetrachloride. They stick, it's a liquid. There are definitely forces there, so what are they? They are dispersion forces and they are based on what we say, our temporal dipole moments. Temporary dipole moments are when the electrons within the entire molecule are in such a flux that at any given moment you are We will trap it with a slightly positive ending and a slightly negative ending and another model, Pikul, will be trapped at that same moment and there will be a attraction there, this will change again and again in a very rapid period of time, but the attraction is there, so, it is a very slight attraction, it is not as strong as a permanent dipole, but that is what we call dispersion forces, so they are the three forces together.

We have hydrogen bonds on the top right below the dipole-dipole interaction and a little bit. Next we have dispersion forces, those are the three main intermolecular forces at play with all molecular substances. We can go into detail about each one, that's another story, so for now, let's keep it clear what the three types are so that when we talk about them. at least you'll know what we're talking about