Periodic Table Evolution

Lorena Miranda II- Camia

Scientists

Antione Lavoisier

1778

He wrote the first extensive list of elements containing 33 elements & distinguished between metals and non-metals

Jakob Berzelius

1828

He developed a table of atomic weights & introduced letters to symbolize elements

Johann Dobereiner

1829

He proposed the Law of Triads: the middle element in certain triads had an atomic weight that was the average of the other two members. He began grouping elements based on similarities. He discovered that calcium (atomic weight 40), strontium (atomic weight 88) and barium (atomic weight 137) had similar properties, and that strontium had an atomic weight halfway between calcium and barium. He discovered it was the same for lithium, sodium, and potassium.

John Newlands

1863

He ordered 62 known elements in order of increasing atomic weight. He noticed that after eight elements occurred, the ninth element displayed similar properties to the first one. He wrote a paper saying that each element showed similar properties to the eighth element following it. He created the Law of Octaves: Elements exhibit similar behaviour to the eighth element following it in the table.

Lothar Meyer

1864

He develops an early version of the periodic table, with 28 elements organized by valence

Dmitri Mendeleev

1869

Ordered elements by atomic weights and properties (Lothar Meyer independently reached a similar conclusion, but his was published after Mendeleev's). The table contained 17 columns, two partial periods with 7 elements in each and two nearly complete periods.

Dmitri Mendeleev

1871

He changed the table, giving it 8 columns. This table showed diagonal, vertical and horizontal relationships between elements. It contained gaps where Mendeleev predicted new elements would be discovered. His Periodic Table included the 66 known elements organized by atomic weights.

William Ramsey

1894

He discovered the Noble Gasses

Henry Moseley

1913

He determined the atomic number of each of the elements and modified the 'Periodic Law'. Moseley arranged elements by atomic numbers, not mass, which removed some of the inconsistencies with Mendeleev's table.

Glenn Seaborg

1940

He experimented with plutonium and discovered the transuranium elements, numbers 94-102 and changed the periodic table by putting them at the bottom.