Dobereiner's Triads

In 1829, J.W. Dobereiner, a German chemist made groups of three elements each and called them triads. All three elements of a triad were similar in their physical and chemical properties. He proposed a law known as Dobereiner's law of triads.

According to this law, when elements are arranged in order of increasing atomic mass, the atomic mass of the middle element was nearly equal to the arithmetic mean of the other two and its properties were intermediate between those of the other two.

This classification did not receive wide acceptance since only a few elements could be arranged into triads.