John Dobereiner was a German scientist who advanced the Law of Triads. Each feature was a group of three elements very much like each other. In 1829, he recorded bromine, an element that dropped about halfway between chlorine and iodine in atomic weight, also show halfway between them. Other “triads” that he identified were: calcium, strontium, and barium, and sulphur, selenium, and tellurium. Shortly, the boundary's were blurred, creating confusion, and these triads were treated like coincidences.