Precursor

{
  "id": "MLC-T-CHM-009361",
  "term": "Precursor",
  "field": "Chemistry",
  "definition": "A nuclide that precedes another nuclide in a radioactive decay chain. The precursor undergoes radioactive decay, transforming into a specific daughter nuclide, which may itself be radioactive and act as a precursor for a subsequent nuclide in the series. For example, in the uranium-238 decay series, thorium-234 is the immediate precursor to protactinium-234.",
  "subject": "Analytical Chemistry",
  "see_also": [
    "decay chain",
    "nuclide",
    "radioactive"
  ],
  "references": [
    "PAC, 1994, 66, 2513. 'Nomenclature for radioanalytical chemistry (IUPAC Recommendations 1994)' on page 2523 (https://doi.org/10.1351/pac199466122513)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/precursor/"
}