Dmitri Mendeleev From the vast amount of experimental data available from the previous chemists he determined that: “Chemical properties of the elements vary periodically with increasing atomic mass” In 1869 devised a periodic table by:- Arranging elements with similar properties into columns (groups)- Arranging elements in order of increasing relative atomic mass into rows (periods) Jons Berzelius Gave the elements their various symbols Synthesized many compounds Isolated and Purified many of the common elements Calculated accurate relative atomic masses (published this in 1828)