Threshold energy

{
  "id": "MLC-T-CHM-013655",
  "term": "Threshold energy",
  "field": "Chemistry",
  "definition": "The minimum kinetic energy that colliding reactant molecules must possess along their line of centers for a chemical reaction to occur upon collision. This energy is required to overcome repulsive forces and to deform molecules sufficiently to allow for bond breaking and bond formation. Threshold energy is a microscopic quantity for a single collision event, whereas activation energy is a macroscopic, empirically determined parameter for a bulk system.",
  "subject": "Physical and Biophysical Chemistry",
  "see_also": [
    "critical energy",
    "reactant",
    "transition state"
  ],
  "references": [
    "Green Book, 2nd ed., p. 56 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)",
    "PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 189 (https://doi.org/10.1351/pac199668010149)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/threshold-energy/"
}