When sodium reacts with oxygen what is the product n is it exothermic or endothermic reaction!?!?

Dear Student, The reaction involved is 4Na (s) + O2 (gas) -----> 2Na2O (s). The product is sodium oxide (Na2O). In this sodium loses electrons to form Na+ and oxygen atoms gain those electrons to form O2- (oxide) ion. As, both the ions are stable, the reaction of formation of Na2O is exothermic. Regards