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1922 BCE
Niels Bohr
Bohr developed the Bohr model of the atom, in which he proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level (or orbit) to another. -
1896 BCE
JJ Thomson
J. J. Thomson, who discovered the electron in 1897, proposed the plum pudding model of the atom in 1904 before the discovery of the atomic nucleus in order to include the electron in the atomic model. In Thomson's model, the atom is composed of electrons. -
1895 BCE
Ernest Rutherford
Ernest Rutherford, 1st Baron Rutherford of Nelson was a New Zealand chemist who has become known as the. In 1911, he was the first to discover that atoms have a small charged nucleus surrounded by largely empty space, and are circled by tiny electrons, which became known as the Rutherford model (or planetary model) of the atom. He is also credited with the discovery of the proton in 1919, and hypothesized the existence of the neutron. He was awarded the Nobel Prize in Chemistry in 1908 -
1776 BCE
John Dalton
John Dalton was an English chemist, physicist, and meteorologist. He is best known for his pioneering work in the development of modern atomic theory; and his research into colour blindness, sometimes referred to as Daltonism, in his honour. -
1200 BCE
Alchemists
The most persistent goals of alchemy have been the prolongation of life and the transmutation of base metals into gold. It appears that neither was accomplished, unless one credits alchemy with the consequences of modern chemotherapy and the cyclotron. -
460 BCE
Demococritus
According to Democritus, the atoms had shape, mass, and motion but no other qualities, such as color or flavor. These latter were supplied by the observer and were subjective
