Valence electrons are defined as

• A. The total number of electrons in the atom.
• B. The number of electrons on the last shell/orbit of the atom.
• C. The energy level of the outermost electron.
• D. The number of protons in the nucleus.

Answer: (B)

Valence electrons are the electrons in the outermost energy level of an atom—the ones farthest from the nucleus and most involved in bonding. Because they sit in the outer shell, these electrons are the ones that can be gained, shared, or lost when atoms form compounds, which is why their count helps determine how many bonds an atom can form and how it behaves chemically. This is why describing valence electrons as the number of electrons on the last shell best captures their role. The total number of electrons in the atom includes inner shells too, not just the outermost shell. The energy level of the outermost electron describes its energy value rather than how many electrons reside in that shell. The number of protons in the nucleus is the atomic number, not the valence electron count.