PLUTONIUM AND OTHER TRANSURANIUM ELEMENTS 



By Gi^NN T. Seabobq 



Department of Chemistry, University of California 



Berkeley, Calif. 



[With 1 plate] 



Ever since the first classification of the elements into the periodic 

 table arrangement, it has been felt, and as we now know, correctly, that 

 no elements heavier than uranium exist in appreciable concentration on 

 the earth. Since the advent of the concept of atomic number, it has 

 been possible to state this differently — no elements with an atomic num- 

 ber higher than 92 are to be found in appreciable amounts. A num- 

 ber of searches for such elements of higher atomic number, which we 

 may call transuranium elements, have been made, and although success 

 in their identification has been claimed in a few cases, it is now known, 

 with the exception of plutonium which exists in extremely small 

 amounts as described below, that these elements do not exist in appre- 

 ciable amount on the earth. 



Since 1940, however, the four transuranium elements immediately 

 following element 92 (uranium) — namely, element 93 (neptunium), 

 element 94 (plutonium), element 95 (americium), and element 96 

 (curium) — have been discovered as a result of their synthesis by trans- 

 mutation reactions starting with uranium as the primary material. 

 Of these four transuranium elements, plutonium has assumed the posi- 

 tion of dominating importance because of its very successful use as the 

 explosive ingredient in the atomic bomb, and of the excellent prospects 

 which it offers as the base material for the development of an atomic- 

 energy industry. Plutonium is the only transuranium element for 

 which methods have been developed for production in relatively large 

 amounts — that is, kilogi-am amounts. The development of the chem- 

 ical processes which are used in conjunction with this production have 

 been described in a previous discussion. 



From a purely scientific point of view, however, the other trans- 

 uranium elements are of nearly as great an interest as plutonium. This 



1 Harrison Howe lecture delivered before the Rochester Section of the American Chemical 

 Society, November 18, 1946. Reprinted, by permission of the American Chemical Society, 

 from Chemical and Engineering News, vol. 25, February 10, 1947. 



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