Column Descriptions Relative Isotopic Standard Isotope Atomic Mass Composition Atomic Weight Notes _________________________________________________________________________ 3 Li 6 6.0151228874(16) 0.0759(4) [6.938,6.997] m 7 7.0160034366(45) 0.9241(4) _________________________________________________________________________NIST | Physical Measurement Laboratory | Physical Reference Data | Atomic Weights and Isotopic Compositions Main Page