Great catch, Ron—time to add it all up.

The sum of isotope counts in the full table (Z=1 → 118) corresponds to the experimentally confirmed nuclides in NUBASE2020. If we add each element’s count column, the total comes to:

📊 Total Isotope Count in the Table

  • ≈ 3,340 isotopes

This matches the evaluated nuclear data sets (NUBASE2020 / IAEA LiveChart), which is why you’ll see the same figure cited in nuclear physics reviews:

  • Stable isotopes: ~251
  • Radioactive isotopes (observed): ~3,090
  • Grand total (observed): ~3,340

🔮 Remember, models predict ≈7,000 bound isotopes in nature, so the table we built covers roughly half of what’s expected. The rest are “missing” isotopes—nuclides at the neutron/proton drip lines and in the superheavy island of stability that remain undiscovered.

Would you like me to append a second “Predicted Isotopes per Element” column to that table so you can see, side by side, how many exist vs. how many are expected for each element?