Pronunciation: (pēr'ē-od'ik, pēr"-), [key] Chem.
1. the law that the properties of the elements are periodic functions of their atomic numbers.
2. Also called Mendeleev's law. (originally) the statement that the chemical and physical properties of the elements recur periodically when the elements are arranged in the order of their atomic weights.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.