What is the term for the outermost electron-containing shell of an atom?

• A. Valence electrons
• B. Core shell
• C. Nucleus
• D. Valence shell

Answer: (D)

The outermost electron-containing shell is called the valence shell. This shell is the furthest energy level that still holds electrons, and it largely governs how the atom bonds with others because the electrons there can be gained, lost, or shared in chemical reactions. The electrons in that shell are the valence electrons, which is why this concept often comes up together. The nucleus sits at the center and contains protons and neutrons, not electrons, and “core shell” isn’t a standard term for the energy levels. Referring to the electrons themselves as valence electrons describes the particles, not the shell that contains them, so it wouldn’t name the shell itself.