Average atomic weight: 6.938–6.997 u
| Isotope | Fraction | Atomic weight/u |
| 6 | 0.0759(4) | 6.0151228874(16) |
| 7 | 0.9241(4) | 7.0160034366(45) |
Atomic weights and isotopic compositions were obtained from NIST Database 144
Li I (Li-like): 130 levels, 1204 lines (E1: 1198 IC: 6), transition probabilities for 756 lines
Li II (He-like): 90 levels, 800 lines (E1: 691 IC: 108 M1: 1), transition probabilities for 794 lines
Li III (H -like): 100 levels, 820 lines (E1: 820), transition probabilities for 820 lines
(Atomic Line List v3.00b5)
