Atomic Weights and Isotopic Compositions for Lanthanum
Isotope
Relative
Atomic Mass
Isotopic
Composition
Standard
Atomic Weight
Notes
57
La
138
137.907 1149(37)
0.000 8881(71)
138.905 47(7)
g
139
138.906 3563(24)
0.999 1119(71)