Why do intermolecular forces tend to attract?

1 Answer
Nov 10, 2015

It's kind of an evolutionary question if you ask me.

Some examples of intermolecular/interatomic forces:

  • Proteins tend to be enthalpically stabilized through the attractive H-bonding interactions which refine their tertiary structure.
  • Stronger attractive intermolecular forces increases boiling point.
  • Attractive interatomic interactions lead atom pairs into forming a bond.

If there were no attractive intermolecular forces, we would probably literally fall apart.

But if you want a more scientific answer to this, you could say that the following is syllogistically true:

1. All molecular systems favor the lowest energy state because...

2. ...the lower the energy state, the more stable the system, and stability tends to be good.

This is commonly reflected in formation of valence electron octets.

3. Attractive forces tend to form enthalpically favorable interactions, because...

4. ...the forming of an interaction releases energy from the system, facilitating the minimization of energy in the system.

The release of energy is shown in the negative sign in the enthalpy of bond formation, which might be notated as #DeltaH_"bond"#.

5. Therefore, most if not all attractive intermolecular forces are favorable.