Illustrated Glossary of Organic Chemistry

Atomic radius: The radius of an atom. This distance between an atom's nucleus and outer electron shell. (This is not a fixed entity, so there are numerous definitions of this term, depending upon the measurement used.) Atomic radius differs with the bonding state of an atom (for example an nonbonded atom of an element versus the same element within a covalent bond). Atomic radius influences many physical and chemical properties, such as polarizability, nucleophilicity, London forces, etc.

Empirical radii for atoms in covalent bonds of the elements in picometers (pm) with an accuracy of 5 pm. (The values for He through Xe column are for the free atoms.) Note the trends in atomic radius within the periods (rows) and families (columns) of the periodic table. No number is present where no data is available.