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Isaac Newtown
Isaac formulated a theory of light , 3 laws of motions and proposed a mechanical universe with small, solid masses in motion. With his contributions we now know that atoms are held together by attractions that we call forces and that stated that matter is formed of solid massy impenetrable particles -
John Dalton
Dalton stated that matter was made up of tiny invisible particles which were called atoms. Atoms could join together to form molecules in a regular predictable way. He also found out that atoms can’t be broken into smaller particles, atoms of the same element are alike and Atoms join together in fixed ratios. His contributions led us to believe that all matter is composed of tiny particles called atoms. Atoms of the same element are alike. -
George Johnstone Stoney
Stoney introduced the term electron and estimated the charge carried by a single hydrogen atom. This was a significant discovery as now we know that atoms can have a negative charge. -
Joseph John Thomson
Thomson discovered tiny negative charged particles known as electrons. He also discover isotopes, Because of his discoveries we know that electrons make up an atom and have negative charges. -
Max Planck
Max Planck explained glowing hot water using the idea of discrete unit of energy and invented the Quantum theory This changed the nature of physics by proving the idea and nature of radiation and energy wrong. -
Hantaro Nagaoka
Hantaro Nagaoka assumed that the model of an atom was “Saturnian” with flat rings of electrons revolving around a positively charged particle. He also created a wrong atom model Becasue of this we have a better understanding of the structure of an atom. -
Robert Andrews Millikan
Millikan experimented with an oil drop to determine the charge and the mass of an electron. His contribtuions allowed us to measure the charge of an electron. -
Ernest Rutherford
Ernest Rutherford discovered positive charged particles which he named protons. And that atoms contained a dense nucleus containing all its positive charge. This discovery confirmed that proton make up an atom and have positive charges. -
Henry Gwyn – Jefferys Mosely
Mosely used X-ray spectra to study atomic structure. His disocvered that each nucleus was characterised by an atomic number equal to the number of unit positive charges associated with it. Using his information the periodic table was arranged according to atomic number rather than atomic weight, a more systematic arrangement was obtained. -
Niels Bohr
Niels Bohr works on light led him to suggest that the electrons didn’t spiral into the nucleus because they weren’t arranged in layers or shells. Electrons could circle a nucleus without radiating energy only in orbits. ---->Shell model This contributed to our understanding of the atom because it told us that nucleus has no electrons and the electrons circle the nucleus. -
James Chadwick
James Chadwick discovered a third particle, the neutron This tells us that neutrons make up an atom -
Democritus
Democtius argued that atoms were the building blocks of matterand that matter was composed of tiny particles called atoms. They could join up with other atoms to create more atoms. This allowed us to understand that atoms existed and that when atoms join up with a certain no of other atoms they form molecules.
