Valence electrons are the electrons in the outermost energy level.

• A. Protons in the nucleus
• B. Electrons in the inner shells
• C. Neutrons in the nucleus
• D. Electrons in the outermost energy level

Answer: (D)

Valence electrons are the electrons in the outermost energy level. They sit in the outer shell, which is the most accessible to other atoms, so these electrons are the ones involved in chemical bonding. Atoms gain, lose, or share these outer electrons to form bonds, and the number of valence electrons largely determines an element’s reactivity and bonding behavior. Electrons in inner shells stay closer to the nucleus and are called core electrons, while protons and neutrons are in the nucleus and don’t participate directly in bonding. So describing valence electrons as those in the outermost energy level captures their location and their role in bonding, with examples like sodium having one valence electron and chlorine having seven.