Which of the following best describes valence electrons and explains their importance in chemistry?

• A. Valence electrons are protons in the outer shell; they determine the atom's charge.
• B. Valence electrons are the electrons in the innermost shell; they do not participate in chemical bonding.
• C. Valence electrons are the electrons found in the nucleus of an atom; they are responsible for the atom's mass.
• D. Valence electrons are the electrons in the outermost shell of an atom; they determine the atom's chemical reactivity and ability to form bonds.

Answer: (D)

Verified step by step guidance

1. Understand that valence electrons are the electrons located in the outermost shell (energy level) of an atom.
2. Recognize that these valence electrons are crucial because they are the ones involved in chemical bonding and reactions.
3. Recall that protons are positively charged particles found in the nucleus and do not participate directly in bonding.
4. Note that electrons in inner shells (core electrons) generally do not participate in chemical bonding because they are held more tightly by the nucleus.
5. Conclude that valence electrons determine an atom's chemical properties and reactivity, as they can be gained, lost, or shared to form chemical bonds.