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| Ion | No. of levels |
|---|
| Nb I | 395 |
| Nb II | 354 |
| Nb III | 189 |
| Nb IV | 183 |
| Nb V | 31 |
| Nb VI | 105 |
| Nb VII | 32 |
| Nb VIII | 2 |
| Nb IX | 2 |
| Nb X | 2 |
| Nb XI | 2 |
| Nb XII | 2 |
| Nb XIII | 2 |
| Nb XIV | 2 |
| Nb XV | 50 |
| Nb XVI | 2 |
| Nb XVII | 2 |
| Nb XVIII | 2 |
| Nb XIX | 2 |
| Nb XX | 2 |
| Nb XXI | 2 |
| Nb XXII | 2 |
| Nb XXIII | 2 |
| Nb XXIV | 2 |
| Nb XXV | 2 |
| Nb XXVI | 2 |
| Nb XXVII | 2 |
| Nb XXVIII | 2 |
| Nb XXIX | 2 |
| Nb XXX | 2 |
| Nb XXXI | 2 |
| Nb XXXII | 2 |
| Nb XXXIII | 2 |
| Nb XXXIV | 2 |
| Nb XXXV | 2 |
| Nb XXXVI | 2 |
| Nb XXXVII | 2 |
| Nb XXXVIII | 2 |
| Nb XXXIX | 20 |
| Nb XL | 80 |
| Nb XLI | 10 |
| Total for Nb: | 1509 |