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460
Democritus 460-370BC
Nationality: Greece
Democritus was the founder of atoms with his partner Leucippus. He belived that there were microscopic things that never die, move, or change. Also he stated that all atoms are alike, which today we know is wrong. -
John Dalton 1776-1884
Nationality: British
Daltons atomic theory had four parts to it.
Dalton atomic theory had four parts to it.
1. All matter has atoms and they are invisible and indestructible.
2. All atoms of a given element are identical
3. Compounds are formed by a combination of two or more different atoms.
4. A chemical reaction is a rearrangement of atoms.
Dalton believed that the atom was a sphere, just like Democritus. His research on atoms was around in 1803 -
Dmitri Mendeleev 1834-1907
Nationality: Russia
Mendeleev was the created of the periodic table of elements. This table has 63 elements, arranged depending on the atomic mass of each element. He created this table in 1869. -
J.J Thomson 1856-1940
Nationality: British
In 1897 Thomson discovered the electron in a series of experiments. Also he suggested a model of an atom as a sphere with positive matter in 1904. -
Ernest Rutherford 1871-1937
Nationality: British and New Zealand
He was the first person to find out that atoms had small charged
nucleuses, and that they are circled by electrons. He also helped with the discovery of protons. He did this from 1909-1911. Lastly he was a student of JJ Thompson. -
Henry Mosley 1887-1915
Nationality: British
Mosley mainly improved the periodic table. He did this by finding more accurate atomic numbers, and which made the position of elements on the table more accurate. He did this in 1913. -
Niels Bohr 1865-1962
Nationality: Denmark
Bohr main contribution to atoms, are mainly theories. The model he created showed, that electrons travel around the outside of the atom's nucleus and electrons can change energy levels. His work was from 1912 to 1922 (only on atoms). -
Louis De Broglie 1892-1987
Nationality: France
His greatest accomplishment was his particle wave theory. He found the electrons wave nature, and proposed that all types of matter have wave properties. He had worked on this from 1922 to 1924. -
James Chadwick 1891-1974
Nationality: British
In 1932 he proved the existence of neutrons. This revolutionary
discovery led Chadwick to help develop the atomic bomb. His work in this area was from 1919 to 1948
