This for metal......the farther to the left the more reactive they are. Group 1 metals, which include sodium and potassium, are so highly reactive that they do not exist in nature by themselves
Thats non metals..........the farther to the right the more reactive they are *with the exception of group 18* which are the noble gases and do not react at all. The most reactive are group 17, which include fluorine and chlorine. These non-metals, like group 1, rarely exist by themselves because of their high reactivity.