Half life

{
  "id": "MLC-T-CHM-005071",
  "term": "Half life",
  "field": "Chemistry",
  "definitions": [
    "The time required for the concentration of a reactant to decrease to half its initial value in a chemical reaction, or for half of the radioactive nuclei in a sample to undergo decay. It is a characteristic constant for a given reaction or radioactive isotope under specific conditions. For first-order reactions, the half-life is independent of the initial concentration.",
    "The time required for the concentration of a reactant to decrease to half of its initial value in a chemical reaction. For a first-order reaction, the half-life is constant and independent of the initial concentration. It is a characteristic parameter for radioactive decay and many photochemical processes."
  ],
  "synonyms": [
    "radioactive half life"
  ],
  "subject": [
    "Physical and Biophysical Chemistry",
    "Organic and Biomolecular Chemistry"
  ],
  "see_also": [
    "lifetime",
    "reactant",
    "stoichiometric",
    "radioactive decay",
    "absorbance",
    "photochromism",
    "wavelength"
  ],
  "references": [
    "Green Book, 2nd ed., p. 55 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)",
    "PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1119 (https://doi.org/10.1351/pac199466051077)",
    "PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 167 (https://doi.org/10.1351/pac199668010149)",
    "PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 975 (https://doi.org/10.1351/pac199668040957)",
    "PAC, 1994, 66, 2513. 'Nomenclature for radioanalytical chemistry (IUPAC Recommendations 1994)' on page 2520 (https://doi.org/10.1351/pac199466122513)",
    "PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 349 (https://doi.org/10.1351/pac200779030293)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/half-life/"
}