Note:  Do not rely on this information. It is very old.

Periodic Law

Periodic Law. It was first observed in the year 1864 by Newlands that if the elements be arranged in the order of their atomic weights [Atomic Theory], those which showed relationship to one another in their chemical characteristics occurred at regular intervals. These elements were then classified together in groups in accordance with this periodicity, and, after further extension by Mendeleef and Lothar Meyer, the classification received general recognition amongst chemists, and might be said to take the form of law which stated that the chemical and physical properties of the elements are functions of their atomic weights.