![]() The experimental evidence collected during the last few years has strongly supported the view that the α particle is a charged helium atom, but it has been found exceedingly difficult to give a decisive proof of the relation. The Nature of the α Particle from Radioactive Substances Įrnest Rutherford & Thomas Royds, Philosophical Magazine 17, 281-286 (1909) It does, however, illustrate the simple and careful experimental methodology of Rutherford. (I would say "helium nucleus," but Rutherford had not yet discovered the nucleus.) In importance to the development of understanding about the atom, this paper does not rank with those cited above. The selection reproduced below represents the final step in the identification of the α particle as a positively-charged helium atom. Rutherford characterized the α particle in work extending over several years with a variety of co-workers. During the World War, Rutherford discovered that some atoms could be induced to fall apart in a process of artificial transmutation. The experiments which found a physically measurable quantity associated with atomic number were also carried out in his laboratory. His correct interpretation of that scattering led to the realization that most of the mass of an atom is concentrated in a tiny core or nucleus thus it is to Rutherford that we owe the nuclear atom and nuclear physics. Large-angle scattering of α particles was first reported in his laboratory. ![]() But some of his most important work was still ahead. This work was sufficient to earn Rutherford a Nobel Prize in 1908. With Frederick Soddy, he realized that radioactive decay actually tranforms an atom of one element into an atom of a different element. He worked out the time-dependence of radioactive decay and introduced the term half-life. Thomson's laboratory, Rutherford distinguished between two different forms of radioactivity, alpha (α) and beta (β). ![]() No one contributed more than Ernest Rutherford (1871-1937 see portrait at National Portrait Gallery (UK)) to an understanding of radioactivity and its domain, the atomic nucleus, in the early years of the 20 th century. ![]() What is the Alpha Particle? Rutherford Elements and Atoms: Chapter 19 ![]()
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