I have a chemistry book that says "When a bond is formed (of whatever kind), energy is released, and that makes the things involved more stable than they were before"
to start with this, bond formation often will release energy, yes, but not always.
The important part for things to happen (without external energy input) is that
the total system might release energy (into the environment of the system) thereafter
... and only if it did, was this loss of energy stabilizing the system (as it would need exactly this energy lost to be forced back into the system to reverse things)
Pathway for this energy output usually is heat,though other mechanisms of relief might occur (for example, light)
The source of this energy usually is NOT the energy of collision of the respective particles (alone):
this energy of collision mostly is required to get things goin', i.e. overcome the initial "barrier before reaction" (
"activation energy" Ea)
Speaking in terms of classical physics, the source however comes from electrostatics. You've got positively charged nucleii, negatively charged electrons, and the nearer they're allowed to approach , the more energy will be set free.
Now, the how near the electrons are allowed to come depends on a lot of factors (and this picture is highly simplified), but basically that's what chemistry is all about: "stable" (i.e. of low energy) substances will have extremely favourable electron ./. nucleii "arrangements , geometries..."
When quantummechanics comes into picture, there are no well-definded "places" for electrons no longer ( and hence no such thing as "distance nuleus - electron") and the understanding of the fines of the wave functions and their "energy" becomes a bit more complicated.
However, the original picture still holds: even in quantum mechanics, the energy that might be released is a electrostatic effect (not just between point type charges)
regards
Ingo