Nuclide & isotope lookup

Reading a nuclide record

The mass number A is the total number of protons and neutrons. Z is the proton number; N = A − Z. A suffix such as m or m2 identifies a metastable state and is kept distinct from the ground state.

Half-life uncertainties in parentheses refer to the last digits of the quoted value. A leading < or > indicates a limit; ~ indicates an approximate value. Stable and unknown entries are shown explicitly. An energy width in eV, keV or MeV is not a half-life for these calculator inputs.

Decay notation: β⁻ (beta minus), β⁺ (beta plus), EC (electron capture), α (alpha), IT (isomeric transition), SF (spontaneous fission). Percentages and qualifiers are retained from the reference record. Natural abundance is reported as a percentage where available; a missing value is not zero.

Data source and scope

Basic fields are drawn from the same NUBASE / ENSDF-derived reference used by Nuclides. This is a dated snapshot, not a live evaluation service.

For evaluation details and current primary data, consult NNDC ENSDF and IAEA LiveChart. Compare values and their uncertainties before using them in a professional workflow.

The web reference covers basic nuclide properties. Detailed emission spectra, decay chains and extended references are available in the app. Searches run in your browser.