Columns:
- Known= observed isotopes (IAEA/NUBASE2020)
- Stable (strict)= nuclides with no decay detected
- Unstable= Known − Stable
- Predicted= scaled to 7,759 (Neufcourt et al., 2020)
- Gap= Predicted − Known
- Representative nuclear γ (keV)= monitoring lines
- NIST Kα₁ (keV)= characteristic XRF line (Z=6–92)
Frequency conversion: ( f \,[Hz] = E \,[keV] \times 2.418 \times 10^{17} ).
| Z | Elem | Known | Stable | Unstable | Pred. | Gap | Nuclear γ (keV) | NIST Kα₁ (keV) | Context |
|---|---|---|---|---|---|---|---|---|---|
| 1 | H | 7 | 2 | 5 | 17 | 10 | — | — | β-only (³H) |
| 2 | He | 9 | 2 | 7 | 21 | 12 | — | — | noble gas |
| 3 | Li | 11 | 2 | 9 | 26 | 15 | — | — | no strong γ |
| 4 | Be | 12 | 1 | 11 | 28 | 16 | — | — | — |
| 5 | B | 13 | 2 | 11 | 31 | 18 | — | — | neutron capture |
| 6 | C | 15 | 2 | 13 | 36 | 21 | — | 0.277 | XRF Kα₁ |
| 7 | N | 16 | 2 | 14 | 38 | 22 | — | 0.392 | XRF Kα₁ |
| 8 | O | 17 | 3 | 14 | 40 | 23 | — | 0.525 | XRF Kα₁ |
| 9 | F | 18 | 1 | 17 | 43 | 25 | — | 0.677 | XRF Kα₁ |
| 10 | Ne | 19 | 3 | 16 | 45 | 26 | — | 0.849 | noble gas, XRF |
| 11 | Na | 20 | 1 | 19 | 47 | 27 | 1274.5 | 1.041 | ²²Na PET line |
| 12 | Mg | 22 | 3 | 19 | 52 | 30 | — | 1.253 | XRF Kα₁ |
| 13 | Al | 22 | 1 | 21 | 52 | 30 | — | 1.486 | calibration target |
| 14 | Si | 23 | 3 | 20 | 55 | 32 | — | 1.740 | ubiquitous XRF |
| 15 | P | 23 | 1 | 22 | 55 | 32 | — | 2.013 | biochemical |
| 16 | S | 24 | 4 | 20 | 57 | 33 | — | 2.307 | XRF Kα₁ |
| 17 | Cl | 24 | 2 | 22 | 57 | 33 | — | 2.622 | tracer gas |
| 18 | Ar | 24 | 3 | 21 | 57 | 33 | 1293.6 | 2.957 | ⁴¹Ar monitoring |
| 19 | K | 24 | 2 | 22 | 57 | 33 | 1460.8 | 3.312 | ⁴⁰K background |
| 20 | Ca | 24 | 6 | 18 | 57 | 33 | — | 3.691 | bone tracer |
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