Relative hardness

{
  "id": "MLC-T-CHM-010143",
  "term": "Relative hardness",
  "field": "Chemistry",
  "definition": "The absolute hardness of a molecule minus that of a matching reference structure, where absolute hardness is half the gap between the ionization energy and the electron affinity. The quantity tracks the resonance stabilization of cyclic conjugated molecules and is used as an index of aromaticity in theoretical organic chemistry.",
  "subject": "Organic and Biomolecular Chemistry",
  "see_also": [
    "aromaticity",
    "resonance"
  ],
  "references": [
    "PAC, 1999, 71, 1919. 'Glossary of terms used in theoretical organic chemistry' on page 1960 (https://doi.org/10.1351/pac199971101919)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/relative-hardness/"
}