Inertial defect

{
  "id": "MLC-T-CHM-005820",
  "term": "Inertial defect",
  "field": "Chemistry",
  "definition": "The difference Ic minus Ia minus Ib formed from the three principal moments of inertia of a molecule, which is exactly zero for a rigid planar molecule. Vibrations make it slightly positive for real planar molecules, while atoms out of the plane make it negative, so its sign and size show how far a molecule departs from planarity. It is obtained from rotational spectra and is sensitive to isotopic substitution.",
  "subject": "Physical and Biophysical Chemistry",
  "see_also": [
    "moment of inertia"
  ],
  "references": [
    "Green Book, 2nd ed., p. 23 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/inertial-defect/"
}