you can know the metal with low reactivity and the metal with high reactivity from the periodic table, as in metals the Chemical reactivity increases by going down a group, because of the farther down group we go the easier of lose and gain of electrons or the easier the electrons to be given or taken, this caused the chemical reactivity be higher.
- and the chemical reactivity decreases as we go across the period because they want to give away valence electrons, they need more energy to get rid of them.