why energy is released when bond is formed

Hi

Energy is released on formation of Bond. The definition of Bond energy Is :
The amount of energy released when one mole ( one Avogadro's number ) of bonds between the constituent atoms.(in the gaseous state ) of a molecule.It is shown as negative sign ( release of energy ) It is obvious that bond formation process is an exothermic process.

molecules must come together to make new bonds after breaking old ones. the only way that they can come sufficiently close to initiate a chemical reaction is when they collide. but u know two molecules' nuclii repel each other as do their electrons. to really come close together these molecules must overcome these repusions. it is acheived by absorbing energy from the surroundings, or in the sense of the word, energy in the form of heat must be supplied. note that during actual bond formation heat is released (exothermic) or absorbed(endothermic).

But after bond formation,  a much stabler structure is formed , having energy lower than that of the individual atoms, therefore the remainder energy is released.