260 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1959 
The prediction of the chemical properties of elements beyond men- 
delevium seems to be quite straightforward. Element 103 should 
complete the actinide series, and it is expected that elements 104, 105, 
106, etc., will be fitted into the periodic table under hafnium, tanta- 
lum, tungsten, etc. The filling of the 6d electronic shell should be 
followed by the addition of electrons to the 7p shell, with the attain- 
ment of the rare gas structure at hypothetical element 118. It seems 
quite certain that the chemical identification of elements 102 and 
103 will eventually be made by ion exchange, using knowledge of 
their homologs ytterbium and lutetium and other actinide elements. 
Element 102 might be expected to have a stable trivalent oxidation 
state and a somewhat unstable bivalent state which may be of impor- 
tance in the chemical identification of the element. ‘The bivalent state 
of element 102, if it is comparable in stability to the bivalent state of 
ytterbium, may permit a rapid separation of element 102 from the 
other actinide elements by electrolytic or amalgam reduction using 
ytterbium as a carrier. The stability of the bivalent state may be 
reflected in the properties of the metallic state of the element, result- 
ing in an unusually low density and a relatively high volatility. Ele- 
ment 103 might be expected to have only a trivalent oxidation state. 
Element 104 should be exclusively tetravalent in aqueous solution and 
should resemble its homolog hafnium. Element 105 should re- 
semble niobium and tantalum, and to some extent protoactinium, with 
the pentavalent oxidation state expected to be the most important. 
The chemical properties of element 106 can be predicted from those of 
tungsten, molybdenum, and to some extent chromium; thus we might 
expect to find the 1m, Iv, v, and vi oxidation states. Elements 107, 
108, 109, 110, etc., would be expected to have chemical resemblance to 
rhenium, osmium, iridium, and platinum respectively. 
The possibility of preparing transfermium elements by the process 
of multiple neutron capture as a result of intense neutron bombard- 
ment over long periods of time is almost precluded by the fact that 
some of the intermediate isotopes have half-lives so short as to pro- 
hibit their presence in such appreciable concentrations as are required. 
Fortunately, there is another type of nuclear reaction that offers prom- 
ise for the production of elements of higher atomic number than those 
now known. This is the method of bombardment with heavy ions. 
Reactions of this type have already been observed in many laborato- 
ries; isotopes of californium, einsteinium, and fermium have been pro- 
duced by the bombardment of uranium with carbon ions, nitrogen 
ions, and oxygen ions, respectively. These ions can be accelerated 
in conventional cyclotrons. A linear accelerator capable of produc- 
ing substantial beams of all the heavy ions up to neon and, possibly, 
usable beams of ions as heavy as those of argon has been constructed 
