Periodic Table - Timeline

Greek Thinkers 400 BC

Anaxagoras, Leucippus, and Democritus developed the concept of the smallest possible particle referred to as the atom. They thought of 4 main elements; Earth, water, fire and air.

He developed the first extensive element list of 55 substances that cannot longer be divided into a simpler substance. His experiments with oxidation disproved the four main elements.

Antonie Lavoisier 1787

Dobereiner 1820

Discovered how the relative atomic mass of the middle element in a group of three is almost halfway between the lightest and heaviest ones in the group. He called this pattern “triad”. He organized many of the elements that (at the time) were discovered that way. The difference of relative atomic mass between three elements.

Dechancourtis 1860

De Chancourtois was a French scientist and the first to arrange the periodic table considering the atomic weight of elements. This way, he made use of a physical property that can be represented as numbers. The elements were arranged in order of increasing weight. He arranged the elements in a cylinder as a spiral called telluric helix. The helix allowed to see similar elements lined up vertically

Cannizaro 1860

Cannizaro discovered more accurately the atomic weights of the elements. He discovered that by arranging several alkaline metals in certain order, you could deduce the atomic weight.

He proposed his “law of octave” in 1864 which organized the known elements into a table by weight. He was one of the first scientists to discover a periodic pattern. He discovered that by arranging the elements by atomic mass, they shared similar properties every 7 elements.

Newlands 1864

Meyer 1870

Meyer published in 1870 a periodic table. His table displayed relationships between atomic number and volume. It clearly showed connectionsbetween elements by chemical properties.

Mendeleyev 1969

Mendeleyev made a periodic table mostly based on chemical properties of elements rather than just atomic mass. He also created a law that would explain were elements would be placed, and predicted a few other elements that had not been discovered like aluminium.

Moseley 1913

He demonstrated major chemical and physical properties are not determined by atomic weight , but by atomic number. Protons determine the atom's identity

These three creative scientists proposed a 3D periodic table using spirals that align vertically with other elements that have similar properties. They aimed for a better education tool to arrange elements with the more possible patterns.

Seaborg 1961

He identified more than 100 isotopes that were placed in the periodic table (with collaborators). He also discovered transuranium elements. He developed the method of isolation to place heavy elements in the periodic table, known as the actinide concept.

Courtines, Gamow and Alexander 1928-1970

2000 years Gap