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Democritus
Democritus discovered that everything was composed of atoms, and this helped the devlopment of modern atomic theory, becaus without this knowledge we would never know what things were composed of. -
Newton
Newton suggested that atoms were held together by "bonds". Without this knowledge, there would not be covalent bonds, ionic bonds. etc. -
Dalton
Dalton proposed the existence of atoms. Although he only lsited 6 elements, he proposed weights for them. Dalton's idea was one of the most influential in modern science. Without this knowledge, we would probably never have known about a few elements and their weights. -
G.J. Stoney
Stoney's most known work was the conception and calculation of the magnitude of the "atom of electricity". In 1891, he proposed the term "electron" to describe the fundamental unit of electrical charge. -
J.J Thomson
Until 1897, most scientists believed that atoms were indivisble, but Thomson proved them wrong. -
Max Planck
He is considered to be the founder of the quantum theory. -
Nagaoka
Nagaoka rejected Thomson's model ont he fround that oppositve charges are impenetrable. Soon after, he proposed a different model in which a positively charged center is surrounded by a number of revolving electrons. -
Millikan
Millikan discovered the mass and charge of the electron. In order to do this, he built a spray that was able to spray oil droplets, as the droplets came out of the nozzle they would become electrically charged by friction. -
E. Rutherford
Physicists knew that the atom contained both positive and negatives charges in equal numbers, however they didn't know how they were distributed. Rutherford tried firing a narrow stream of alpha particles at a thin gold foil, and detecting where they came out. He suspected the particles would go through the foil but some would be deflected by passing close to an electron in the atom. -
H.G.J. Moseley
Moseley found that atoms of each element contain a unique positive charge in their nucleus. This discovery helped solve the mystery of what makes the atoms of one element different to another. -
Bohr
Bohr put forward his picture of the atom in 1913. He used Plank's quantum theory and also suggested that electrons can only have certain amounts of energy, and their orbit can have a certain radius. -
James Chadwick
In 1932, Chadwick discovered that the particle in the nucleus of an atom that became known as the "neutron" has no electric charge.