Atomic number: 4 Symbol: Be
Average atomic weight: 9.012182(3) u
| Isotope | Fraction | Atomic weight/u |
| 9 | 1.0000(0) | 9.0121822(4) |
Atomic weights and isotopic compositions were obtained from NIST Database 144
Be II (Li-like): 217 levels, 2844 lines (E1: 2844), transition probabilities for 789 lines
Be III (He-like): 194 levels, 1945 lines (E1: 1935 IC: 10), transition probabilities for 1784 lines
Be IV (H -like): 100 levels, 824 lines (E1: 824), transition probabilities for 824 lines
(Atomic Line List 2.05b16, compiled on Jan 13, 2012)