How can you predict the intermolecular forces that would be given a particular molecule?

Answer 1

That will depend on the electronegativity of the atoms involved and the size of the atoms that constitute the compound. There are 3 types of intermolecular forces.

Firstly, we have the permanent dipole-permanent dipole interaction. The dipole-dipole interaction is a result of permanent dipoles that exist within the molecule. This is caused by the difference in electronegativity between the 2 atoms. When chlorine meets hydrogen, the highly electronegative chlorine will pull the electrons that is in the covalent bond towards itself, thus forming a delta+ charge at hydrogen and delta- over at chlorine. So, when one highly electronegative atom bonds with a way less electronegative atom, this interaction will occur.

Secondly, we have the induced dipole-induced dipole interaction. When 2 atoms meet, electrons repel each other due to the close proximity. Thus, it forms a delta- charge at 1 end of the atom while leaving the other end with a delta+ charge. Plus, electrons move in orbitals, and there are times when they will congregate at one side of the atom. This movement of electrons causes delta- charge to occur at different parts of the atom. Larger atoms are more likely to go through this type of interaction because they have more electrons and hence a higher chance of having congregation.

Thirdly, hydrogen bonding occurs when hydrogen (low in electronegativity) bonds with a highly electronegative atom, such as nitrogen, oxygen and fluorine. This causes the same effect as the permanent dipole-permanent dipole interaction, but is characterized by the interaction between hydrogen and a highly electronegative atom. Thus, if the molecule is constituted by these few atoms, such a intermolecular force is likely to act on it.