The New Chemical Elements' 



By Saul Dushman 



Research Consultant, General Electric Research Laboratory, Schenectady, N. Y. 



All matter, mineral and organic, is made up of combinations or 

 mixtures of elementary substances known as chemical elements. 

 Before 1937 about 88 such elements had been found. About 30 of 

 these elements occur on the earth, in the free or chemically uncombined 

 state. Examples of such elements are : the gases hydrogen, oxygen, 

 nitrogen, and argon, which occur in the atmosphere; the metals gold, 

 platinum, silver, copper, and mercury ; and the nonmetals carbon and 

 sulfur. Each chemical element is made up of infinitesimally small 

 corpuscles, which were originally designated atoms, because they were 

 assumed to be indivisible. The atoms of any one element are the 

 same in size, mass, and chemical properties. If we assign to the atom of 

 the lightest element (that is, hydrogen) the atomic weight 1, then the 

 atomic weight of uranium — until 1940 the heaviest known element — 

 is 238. The diameters of atoms of the different elements vary from 

 about one hundred-millionth of an inch to about three times that value. 



About 50 years ago it was discovered that white-hot metals, when 

 negatively charged, emit electrons. These have been shown to be 

 extremely small particles each of which carries a unit charge of 

 negative electricity and has a mass about 2,000 times smaller than 

 that of the hydrogen atom. The diameter of the electron is about 

 one hundred-thousandth of that of an atom. Also, at about the same 

 time, the phenomenon of radioactivity was discovered ; that is, it was 

 observed that certain high-atomic-weight elements disintegrate 

 spontaneously into elements of lower atomic weight. Thus it was 

 recognized during the first decade of the present century that the 

 atom is not a simple, spherically shaped little mass, without structure, 

 but must be composed of still more elementary particles, which govern 

 the observed chemical and physical properties of the different chemical 

 elements. 



1 Talk presented at the General Electric Science Forum broadcast on December 27, 1950. 

 Reprinted by permission from General Electric Review, vol. 54, No. 4, April 1951, with 

 som« revision by the author. 



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