<span>When chemical reactions take place, chemical bonds are broken in the reactants and new chemical bonds are formed in the products. It is as a result of these processes that a reaction is overall exothermic (energy is given out to the surroundigs) or overall endothermic (energy is absorbed from the surroundings hopefully this helped :)</span>
The oxidation number for ba is -2
Elements are used to create bonds and are classified as particles.
I think a good strategy for these kind of problems is to just choose the atom with the highest mass number. At any rate, the answer actually is (and I guessed it as) (2) Francium-220. It has a half life of about 30 seconds.