please explain to me the energies of each step in free radical addition (if possible with a diagram)ALSO EXPLAIN TO ME THE TYPE OF REACTION OF INITIATION..PROPAGATION AND TERMINATION STEP..THAT IS WHETHER IT IS EXOTHERMIC OR ENDOTHERMIC????

The reaction is done at high pressures in the presence of a trace of oxygen as an initiator.

The function of the oxygen - chain initiation

The oxygen reacts with some of the ethene to give an organic peroxide. Organic peroxides are very reactive molecules containing oxygen-oxygen single bonds which are quite weak and which break easily to give free radicals.

You can short-cut the process by adding other organic peroxides directly to the ethene instead of using oxygen if you want to.

You don't need to worry about the exact formulae of the free radicals which start the reaction off - they vary depending on their source. For simplicity we give them a general formula: Ra