Flexi Says: In 1829, a German chemist, Johann Dobereiner (1780-1849), placed various groups of three elements into groups called triads. One such triad was lithium, sodium, and potassium. Triads were based on both physical as well as chemical properties. Dobereiner found that the atomic masses of these three elements, as well as other triads, formed a pattern. When the atomic masses of lithium and potassium were averaged together , it was approximately equal to the atomic mass of sodium (22.99). While Dobereiner’s system would pave the way for future ideas, a limitation of the triad system was that not all of the known elements could be classified in this way.English chemist John Newlands (1838-1898) ordered the elements in increasing order of atomic mass and noticed that every eighth element exhibited similar properties. He called this relationship the “Law of Octaves.” Unfortunately, there were some elements that were missing and the law did not seem to hold for elements that were heavier than calcium. Newlands’s work was largely ignored and even ridiculed by the scientific community in his day. It was not until years later that another more extensive periodic table effort would gain much greater acceptance and the pioneering work of John Newlands would be appreciated.