The History and Progression of Chemistry The birth of the modern atomic theory. In 1750, Rudjer Boscovich, a scientist born in what is now Croatia, suggested the theory that atoms were "uncuttable" might have been wrong. Boscovich thought that atoms contain smaller parts, which in turn contain still smaller parts, and so forth down to the fundamental building blocks of matter. He felt that these building blocks must be geometric points with no size at all. …showed first 75 words of 653 total…

…showed last 75 words of 653 total…similar properties appear at regular intervals, or periods, in the table. The two chemists rearranged the table in columns so that elements with similar properties were grouped together. Such an arrangement became known as the periodic table. Both men left gaps in the table, and Mendeleev correctly predicted that elements with certain properties would be discovered to fill the gaps. The modern periodic table serves as a guide to the chemistry of all known elements.