| Period | 1 | 2 | 3 | 4 | 5 | 6 | 7 | ||||||
| Subshells | 1s | 2s | 2p | 3s | 3p | 4s | 3d 4p | 5s | 4d 5p | 6s | 4f 5d 6p | 7s | 5f 6d 7p… |
| Order | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | |||||