sir exothermic reactions are energy releasing reactions, right? and also endothermic reactions are energy gaining reactions . so when binding energy of the reactent molecules is less than the binding energy of the product, then how it became the exothermic reactions . sir pls check the attachment from ncert?sir pls give me the answer …......?

If we consider a nuclear reaction,
Check out the Nuclear Binding Energy Curve at wikipedia (link below). If you turn the graph upside down, it shows the energy per nucleon of almost every element in the period table left to right, with hydrogen on the left and uranium on the right.

Notice how iron (=Fe) has the lowest energy per nucleon.

Nuclear fission is splitting a nucleus up into one or more smaller nuclei. For example, if a uranium nucleus could be split into any of the elements between iron and uranium, each nucleon would have less energy according to the graph. Energy has left the system, making this an exothermic reaction.

Nuclear fusion is joining nuclei together. For example, if hydrogen nuclei could be joined into any of the elements between hydrogen and iron, each nucleon would have less energy according to the graph. Again, energy has left the system, making this an exothermic reaction.

You could get endothermic nuclear fission by starting with an element between hydrogen and iron, and ending up with hydrogen. Likewise, you could get endothermic nuclear fusion by starting with and element between iron and uranium and ending up with uranium.

Just because a reaction is exothermic, does not mean it is easy for us to make it happen. Nuclear fusion takes HUGE temperatures to initiate, which has so far kept us from building nuclear fusion power plants (existing nuclear plants use nuclear fission).

Approved