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Sir J.J. Thomson
He demonstrated that cathode rays were negatively charged. In addition, he also studied positively charged particles in neon gas. Thomson determined that all matter is made up of tiny particles that are much smaller than atoms. This led to one of his other famous discoveries in 1912, when he channeled a stream of ionized neon through a magnetic and an electric field and used deflection techniques to measure the charge to mass ratio. -
Lord Rutherford
Ernest Rutherford 1871-1937 set forth the laws of radioactive decay,and identified alpha particles as helium nuclei.Most importantly, he postulated the nuclear structure of the atom.Rutherford overturned Thomson's model in 1911 with his well-known gold foil experiment in which he demonstrated that the atom has a tiny and heavy nucleus.Rutherford designed an experiment to use the alpha particles emitted by a radioactive element as probes to the unseen world of atomic structure. -
Niels Bohr
Bohr was the first to discover that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element. In 1913, on the basis of Rutherford's theories, Bohr developed and published his model of atomic structure, known as the Bohr model, which depicts the atom as a small, positively-charged nucleus surrounded by negatively-charged electrons that travel in circular orbits around the nucleus, -
Sir James Chadwick
In 1913, Neils Bohr, a student of Rutherford's, developed a new model of the atom. He proposed that electrons are arranged in concentric circular orbits around the nucleus. This model is patterned on the solar system and is known as the planetary model. The Bohr model can be summarized by the following four principles:
