| Proton | Neutron | Nuclear Spin | Energy State | |
|---|---|---|---|---|
| 19Mg | 12 | 7 | -1/2 | |
| 20Mg | 12 | 8 | 0 | |
| 21Mg | 12 | 9 | 3/2 | |
| 22Mg | 12 | 10 | 0 | |
| 23Mg | 12 | 11 | 3/2 | |
| 24Mg | 12 | 12 | 0 | Stable |
| 25Mg | 12 | 13 | 5/2 | Stable |
| 26Mg | 12 | 14 | 0 | Stable |
| 27Mg | 12 | 15 | 1/2 | |
| 28Mg | 12 | 16 | 0 | |
| 29Mg | 12 | 17 | 3/2 | |
| 30Mg | 12 | 18 | 0 | |
| 31Mg | 12 | 19 | 3/2 | |
| 32Mg | 12 | 20 | 0 | |
| 33Mg | 12 | 21 | -7/2 | |
| 34Mg | 12 | 22 | 0 | |
| 35Mg | 12 | 23 | -7/2 | |
| 36Mg | 12 | 24 | 0 | |
| 37Mg | 12 | 25 | -7/2 | |
| 38Mg | 12 | 26 | 0 | |
| 39Mg | 12 | 27 | -7/2 | |
| 40Mg | 12 | 28 | 0 |