He also had the great pleasure of seeing several of his close associates receive their own Nobel Prizes, including Rutherford in chemistry (1908) and Aston in chemistry (1922). Thomson received various honors, including the Nobel Prize in Physics in 1906 and a knighthood in 1908. In 1913 Thomson published an influential monograph urging chemists to use the mass spectrograph in their analyses. The model described the atom as a tiny, dense, positively charged core called a nucleus, in which nearly all the mass is concentrated, around which the light, negative constituents, called electrons, circulate at some. His nonmathematical atomic theory-unlike early quantum theory-could also be used to account for chemical bonding and molecular structure (see Gilbert Newton Lewis and Irving Langmuir). Rutherford model, description of the structure of atoms proposed (1911) by the New Zealand-born physicist Ernest Rutherford. Of all the physicists associated with determining the structure of the atom, Thomson remained most closely aligned to the chemical community. He was a good lecturer, encouraged his students, and devoted considerable attention to the wider problems of science teaching at university and secondary levels. Even though he was clumsy with his hands, he had a genius for designing apparatus and diagnosing its problems. In 1884 he was named to the prestigious Cavendish Professorship of Experimental Physics at Cambridge, although he had personally done very little experimental work. He was then recommended to Trinity College, Cambridge, where he became a mathematical physicist. Instead young Thomson attended Owens College, Manchester, which had an excellent science faculty. His father intended him to be an engineer, which in those days required an apprenticeship, but his family could not raise the necessary fee. Ironically, Thomson-great scientist and physics mentor-became a physicist by default. His assistant, Francis Aston, developed Thomson’s instrument further and with the improved version was able to discover isotopes-atoms of the same element with different atomic weights-in a large number of nonradioactive elements. Here his techniques led to the development of the mass spectrograph. Thomson’s last important experimental program focused on determining the nature of positively charged particles. His efforts to estimate the number of electrons in an atom from measurements of the scattering of light, X, beta, and gamma rays initiated the research trajectory along which his student Ernest Rutherford moved. (c) In the cathode ray, the beam (shown in yellow) comes from the. ![]() ![]() (b) This is an early cathode ray tube, invented in 1897 by Ferdinand Braun. Thomson produced a visible beam in a cathode ray tube. In 1904 Thomson suggested a model of the atom as a sphere of positive matter in which electrons are positioned by electrostatic forces. The results of these measurements indicated that these particles were much lighter than atoms (Figure 3.3.1 3.3. Structure of the Atom and Mass Spectrography
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