An element’s in the periodic table shows its . Each is an energy level. • For most elements, the outermost level is only with electrons. • Electrons in the outermost level are called .  They allow atoms to and form or substances. The number of valence electrons determines how an element reacts with other elements. • For the first 3 rows: To find the number of valence electrons for elements in the first three rows, count how far along in a row the element is, and that number is the number of valence electrons. • Many depend on valence electrons