This is a very good question but probably better asked to a Chemist. I will attempt to answer it for you though. So the driving force behind chemical reactions is all about the rearranging of electrons. All atoms seem to be happier with sets of electrons that make up certain numbers. These numbers is what governs the way the periodic table is laid out. So, for example if you look at the number of electrons that Chlorine has you will see it has 17 electrons to balance its 17 protons. This is not a nice number as far as atoms are concerned. Atoms ‘like’ the numbers 2, 10, 18, 36, etc. So Chlorine would be much happier with one more electron bringing it to 18 electrons. If we then look at Sodium we see it has 11 electrons. Therefore Sodium would like to get rid of one so it would have the nice number 10. So if we mix Chlorine and Sodium together we find that the Sodium atoms give up one of their electrons to the Chlorine atoms so that they are both ‘happier’. But this swapping leaves the Sodium positivly charged and the Chlorine negatively charged. We know positive attracts negative, so the Chlorine atoms attract the Sodium atoms and they kind of stick together. This make Sodium Chloride, also known as Salt. This rearranging of electrons explains ALL chemistry. The atoms either swap, or sometimes share, electrons and these forces drive the reactions!
It often comes down to electrons. Some chemicals have electrons in their atoms that are more eager to join or be shared with other atoms. We can tell how reactive most substances are by looking at the electrons of its atoms.
There are similarities between chemical reactions and nuclear ones. Nuclear reactions that stars typically use are of the “exothermic” variety for chemists, meaning that one gets out more energy than one puts in. This is what makes stars hot and bright.
The difference is that instead of rearranging electrons in the cloud around the nucleus, one is rearranging nucleons (protons, neutrons) in the nucleus (and also changing elements). Since the strong nuclear force is much “stronger” than the electromagnetic force, one can get much greater energy released.