Valence electrons are important because

A) They form chemical bonds with other atoms

B) They tell which period the element is in

C) They take isotopes

D) They identify the element

A) They form chemical bonds with other atoms

Explanation:

In chemistry, a valence electron is an outer shell electron that is associated with an atom, and that can participate in the formation of a chemical bond if the outer shell is not closed; in a single covalent bond, both atoms in the bond contribute one valence electron in order to form a shared pair.