reactivity
Reactivity is how likely an element is to react chemically with other elements. Some nonmetals are extremely reactive, whereas others are completely nonreactive. What explains this variation in nonmetals? The answer is their number of valence electrons. These are the electrons in the outer energy level of an atom that are involved in interactions with other atoms. Lets look at two examples of nonmetals, fluorine and neon. Simple atomic models of these two elements are shown in the Figure below .