Here methane and methane are going to come together to form a liquid. They can do that if the temperature is cold enough of course because the boiling point is very, very low. How they attract it and how they form it intermolecular bond to form a liquid in a solid? Protons and one molecule will attract electrons of another. They still do that. Not just within the individual molecule, but between molecules as well. That force of attraction causes them to come together and you’ve got yourself an intermolecular bond called London Dispersion Force. It’s one of the types of Van der Waals forces.
Here’s another Van de Waals force, if you have two polar molecules—okay, here’s something like HCl. So in HCl you’ve got a partially negative and positive region, well that attracts the partially positive and negative region of another molecule. So when they come together you can form a liquid and a solid this way, as well as attracting by protons and electrons so they still have London Dispersion Force but they also have something called Dipole-dipolar force. So that’s the second type. But you can have a really strong dipole-dipolar force that occurs between molecules like water or ammonia, or HF. Anytime you have hydrogen attached to O or N or F, you’ve got yourself a real high degree of difference in polarity here or electron negativity between the no-metal and the hydrogen. So what happens is you have a really partially positive and negative region established therefore, when these two molecules come together they really form strong bonds, and that’s called a hydrogen bond.
And even a little bit stronger than a hydrogen bond, would be when you have NaCl and that’s an ionic bond and ionic bonds—well take a look, they actually form these lattices or crystals. So NaCl would have this cubicle type of shape to it. The lattice is structured very rigid and it forms very strong bonds. Ionic would be stronger than those other ones. Although we wouldn’t necessarily call it an intermolecular bond and neither would we call metallic bonding. How do metals come together? Well, electrons flip from one empty valence orbital to another inside metallic atoms to create very ductile and very conducting types of structures—metallic structures which are also quite lustrous. This is just about strong as ionic you could say, give or take.
But the strongest bonding in the world, that occurs when you have carbons stacked on carbons. If you take carbons which are piled on top of each other like this in a network, network covalent bonding; carbon here can be compressed to form coal, graphite and then kind of loses its blackness and it becomes very shiny, it turns into diamond. The strongest type of bonding we have.
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