Chapter 37, Problem 1FTD

If you push two atoms together to form a molecule, the exclusion principle results in a repulsive interaction between the atoms. How does this repulsion come about?

To determine

How does the repulsion as a result of exclusion principle come about between two atoms when they are pushed together to form a molecule.

Answer to Problem 1FTD

The repulsive force according to the exclusion principle results from the overlapping of the electrons belonging to the two atoms.

Explanation of Solution

Pauli Exclusion Principle states that no two electrons in an atom or molecule can have the same four electronic quantum numbers. In other words only two electrons can be in the same orbital of an atom or molecule with one electron having spin up and other having spin down.

Although individual atoms are electrically neutral, the distribution of charge within them gives rise to attractive or repulsive forces. The repulsive force results from the overlapping of the electrons belonging to the two atoms. In accordance with the Exclusion principle, two electrons cannot occupy the same state.

Thus when the atoms are pushed together so that electron wave functions would begin to overlap and occupy the same region of space, the electron clouds of the atoms have to be distorted to avoid the violation of the exclusion principle. This will require energy so that work has to be done in bringing them together which implies there exists a repulsive force.

Conclusion:

Thus the repulsive force according to the exclusion principle results from the overlapping of the electrons belonging to the two atoms.