Z Elem Known Stable Unstable Pred. Gap Nuclear γ (keV) NIST Kα₁ (keV) Context 81 Tl 39 2 37 93 54 2614.5 72.871 ²⁰⁸Tl (Th-series) + XRF 82 Pb 43 4 39 102 59 351.9 / 46.5 74.969 ²¹⁴Pb, ²¹⁰Pb γ + XRF 83 Bi 41 0 41 97 56 609.3 / 1120.3 / 1764.5 … Continue reading Master Isotope Table — NIST SRD-128 Kα₁ (Z = 81–100)