What is the distance from the nucleus to the outermost electron?

• A. Ionization Energy
• B. Electronegativity
• C. Atomic Radius
• D. Hydrogen Bond

Answer: (C)

The distance from the nucleus to the outermost electron is described by the atomic radius. Atomic radius is a measure of the size of an atom, essentially how far the outer edge of the electron cloud extends from the nucleus. In practice, different radii definitions exist depending on bonding context (covalent radius for bonded atoms, van der Waals radius for nonbonded interactions, metallic radius for metals), but all of these quantify how big the atom is and how far its outer electrons reach.

This concept is distinct from ionization energy, which is the energy required to remove an electron and tells you how tightly electrons are held rather than how far they sit from the nucleus. It’s also distinct from electronegativity, which describes an atom’s ability to attract electrons in a chemical bond. And hydrogen bonding refers to a specific type of intermolecular interaction, not a measure of an atom’s size. So atomic radius is the term that best answers the question about the distance from the nucleus to the outermost electron.