True. Since in an elementary step , the reaction procedes by collision of the atoms of reactants involved and since the rate of collision is proportional to the concentration of each atom that participates in the elementary step , the exponents in the rate law of the elementary step always coincides with the coefficients that correspond to that reaction ( regardless if is unimolecular, bimolecular or trimolecular).
In a reactivity series, the most reactive element is placed at the top and the least reactive element at the bottom. More reactive metals have a greater tendency to lose electrons and form positive ions .
