ABUNDANCE OF CHEMICAL ELEMENTS—SUESS 313 
Furthermore, one can see that nuclear species containing just such a 
number of neutrons are in general exceptionally abundant (fig. 3). 
These facts indicate that the abundance of nuclear species is deter- 
mined by nuclear properties. The individual abundances of nuclear 
species should therefore form a coherent system of some kind; they 
10 BILLION 
1 BILLION 
100 MILLION 
110 MILLION 
MS 
1 MILLION 
| 
TMT EEE 
SNAG 
JAA EEE 
POW AN EEE 
NUMBER OF NUCLEI OF A GIVEN MASS NUMBER PER MILLION SILICON ATO! 
\ 
CONN 
ELLE FSN LG 
ERGEN 
CTT LETT ev LA 
LUTTE ETT Terr 
MASS NUNBEB" 
Fic. 3.—Abundance of nuclei plotted against their mass number. The upper line refers to 
nuclei with even, the lower line to those with odd, mass number. 
~ 
Ss 
should depend in a similar fashion on the number of protons and 
the number of neutrons in a nucleus. 
We know the relative abundance of nuclei containing the same 
number of protons (isotopes) with great precision from mass- 
spectroscopic measurements, and can expect that all the abundances 
of the nuclear species should in some way be connected with these 
data. This indeed can be shown to be the case. 
