Written by the Fiveable Content Team • Last updated August 2025
Written by the Fiveable Content Team • Last updated August 2025
Definition
Mendeleev was a Russian chemist who created the first version of the periodic table. He arranged elements by increasing atomic mass and predicted the existence and properties of undiscovered elements.
The mass of an atom, typically expressed in unified atomic mass units (u).
Periodic Law: The principle that the properties of the elements recur periodically when the elements are arranged in increasing order by their atomic numbers.