Major Developments in the Periodic Table

Events

Telluric Screw Model

1862

French geologist Alexandre-Emile Béguyer de Chancourtois listed the elements on paper tape and wound them, spiral like, around a cylinder. Certain ‘threes’ of elements with similar properties came together down the cylinder. He called his model the ‘telluric screw’.

Law Of Octaves

1864

English chemist John Newlands noticed that, if the elements were arranged in order of atomic weight, there was a periodic similarity every 8 elements. He proposed his ‘law of octaves’ on this.

Properties with Similar Properties

1869

Russian chemist Dmitri Mendeleev produced a periodic table based on atomic weights but arranged ‘periodically’. Elements with similar properties appeared under each other. Gaps were left for yet to be discovered elements.

Atomic Weight Increases

1869

Lothar Meyer complied a periodic table of 56 elements based on a regular repeating pattern of physical properties such as molar volume. Once again, the elements were arranged in order of increasing atomic weights.

Noble Gases Are Discovered

1894

William Ramsay discovered the noble gases and realised that they represented a new group in the periodic table.

Atomic Numbers

1914

Henry Moseley determined the atomic number of each of the known elements. He realised that, if the elements were arranged in order of increasing atomic number rather than atomic weight, they gave a better fit within the ‘periodic table’.

Actinides

1940

Glenn Seaborg artificially produced heavy mass elements such as neptunium. These new elements were part of a new block of the periodic table called ‘actinides’.