forceðFÞgenerally is the derivative of the energyðF¼dU=dhÞand, as
illustrated in the figure, the net force is thus zero where the energy is at
minimum; here we have a stable configuration.
Table 3.1 gives an overview of the various types of forces. The first one
mentioned cannot lead to bond formation, since it is always repulsive. If two
atoms approach closely, their electron clouds start to overlap, and this
causes a repulsion that increases very steeply with decreasing distance; it is
FIGURE3.1 Hypothetical example of the net energy needed to bring two molecules
or particles from infinite separation to a certain mutual distance, and of the
corresponding interaction force.