Average atomic weight: 24.304–24.307 u
| Isotope | Fraction | Atomic weight/u |
| 24 | 0.7899(4) | 23.985041697(14) |
| 25 | 0.1000(1) | 24.985836976(50) |
| 26 | 0.1101(3) | 25.982592968(31) |
Atomic weights and isotopic compositions were obtained from NIST Database 144
Mg I (Mg-like): 310 levels, 10364 lines (E1: 5394 IC: 4965 M1: 2 E2: 2 M2: 1), transition probabilities for 1416 lines
Mg II (Na-like): 115 levels, 1405 lines (E1: 1128 IC: 277), transition probabilities for 758 lines
Mg III (Ne-like): 111 levels, 1358 lines (E1: 1216 IC: 138 M1: 2 E2: 1 M2: 1), transition probabilities for 136 lines
Mg IV (F -like): 151 levels, 2265 lines (E1: 1635 IC: 628 M1: 1 E2: 1), transition probabilities for 921 lines
Mg V (O -like): 75 levels, 665 lines (E1: 431 IC: 222 M1: 5 E2: 7), transition probabilities for 428 lines
Mg VI (N -like): 110 levels, 1814 lines (E1: 816 IC: 981 M1: 8 E2: 9), transition probabilities for 960 lines
Mg VII (C -like): 85 levels, 725 lines (E1: 421 IC: 292 M1: 5 E2: 7), transition probabilities for 521 lines
Mg VIII (B -like): 102 levels, 974 lines (E1: 931 IC: 40 M1: 1 E2: 2), transition probabilities for 902 lines
Mg IX (Be-like): 86 levels, 1373 lines (E1: 707 IC: 661 M1: 2 E2: 2 M2: 1), transition probabilities for 501 lines
Mg X (Li-like): 57 levels, 586 lines (E1: 476 IC: 110), transition probabilities for 197 lines
Mg XI (He-like): 68 levels, 581 lines (E1: 345 IC: 235 M2: 1), transition probabilities for 246 lines
Mg XII (H -like): 225 levels, 3028 lines (E1: 3028), transition probabilities for 3028 lines
(Atomic Line List v3.00b5)
