How can you predict which element are stable under natural condition and which element tend to under go chemical reaction?

Answer 1

There are two levels of chemical stability, one is whether the reaction in question releases energy in the form of heat or whether it creates more disorder. These two principal factors drive every chemical reaction that one will encounter from cradle to grave (baring any work involving nuclear reactors). They are formally known as entropy (change in disorder) and enthalpy (change in heat). These two factors taken together tell whether a reaction will happen or not (whether it is spontaneous or not). The easy way to find whether the reaction is favorable (spontaneous) or not is to look up the Gibb's free energy (in a table) for the products and the reactants and then subtract the sum of the reactants from the sum of the products. If the number is negative, then the reaction is spontaneous at room temperature. This concept takes quite a bit of work to master and accounts for the bulk of any chemistry text book, so don't expect to learn the answer overnight.