What is the role of valence electrons in chemical bonding?

Valence electrons play a crucial role in chemical bonding because they are the outermost electrons in an atom and are involved in forming bonds with other atoms. Their arrangement determines how easily an atom can react with others to form compounds. Atoms aim to achieve a stable electron configuration, often resembling that of the nearest noble gas, by either gaining, losing, or sharing their valence electrons. This behavior is what underlies the reactivity of elements; for example, alkali metals have a single valence electron that they tend to lose easily, leading to high reactivity, while noble gases are largely unreactive due to their complete valence shells.

The other options do not accurately reflect the primary role of valence electrons in chemical bonding. While valence electrons connect to an atom's reactivity, they do not stabilize the atomic nucleus directly, are not responsible for the atom's mass, and are involved in various bond types beyond just ionic bonds, including covalent and metallic bonds.