Key dates in the history of the Periodic Table
400 B.C.E. - Democritus develops the idea of an atom.
1661 - Robert Boyle pointed out an element cannot be decomposed into simpler substances.
1766 - Hydrogen was discovered by Henry Cavendish.
1778 - Antoine Lavoisier wrote an in depth list of 33 elements, stating whether they were metals and non metals.
1818 - Jons Jacob Berzelius introduced letters to symbolise elements. He also developed a table of atomic weights.
1829 - Johann Wolfgang Dobereiner discovered some elements had similar chemical properties.
1865 - John Newlands arranged the known elements in order of atomic weight and was able to see patterns.
1868 - Lothar Meyer prepared a table (in order of atomic weight) and discussed relationships between properties of elements and atomic weight.
1869 - Mendeleev first presented his periodic table.
1894 - William Ramsay discovered Noble Gases.
1903 - Ernest Rutherford collaborated with Frederick Soddy to show certain heavy atoms decay into lighter atoms.
1913 - Henry Mosely found the positive charge of an atom and referred to it as the atomic number.
1940 - First Transuranium element (neptunium) was discovered by Edwin McMillan.
1941 - Second Transuranium element (plutonium) discovered by Glenn Seaborg.
1661 - Robert Boyle pointed out an element cannot be decomposed into simpler substances.
1766 - Hydrogen was discovered by Henry Cavendish.
1778 - Antoine Lavoisier wrote an in depth list of 33 elements, stating whether they were metals and non metals.
1818 - Jons Jacob Berzelius introduced letters to symbolise elements. He also developed a table of atomic weights.
1829 - Johann Wolfgang Dobereiner discovered some elements had similar chemical properties.
1865 - John Newlands arranged the known elements in order of atomic weight and was able to see patterns.
1868 - Lothar Meyer prepared a table (in order of atomic weight) and discussed relationships between properties of elements and atomic weight.
1869 - Mendeleev first presented his periodic table.
1894 - William Ramsay discovered Noble Gases.
1903 - Ernest Rutherford collaborated with Frederick Soddy to show certain heavy atoms decay into lighter atoms.
1913 - Henry Mosely found the positive charge of an atom and referred to it as the atomic number.
1940 - First Transuranium element (neptunium) was discovered by Edwin McMillan.
1941 - Second Transuranium element (plutonium) discovered by Glenn Seaborg.
Hover over the images to view the scientist's name.