Mass number

{
  "id": "MLC-T-CHM-006985",
  "term": "Mass number",
  "field": "Chemistry",
  "definition": "The total number of protons and neutrons (nucleons) in an atomic nucleus. It is an integer that represents the approximate atomic mass of an isotope. The mass number is denoted by A and is written as a superscript before the element symbol, for example, ¹²C.",
  "subject": "Physical and Biophysical Chemistry",
  "see_also": [
    "mass spectrometry",
    "nucleon number",
    "nucleus"
  ],
  "references": [
    "Green Book, 2nd ed., p. 20 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)",
    "PAC, 1991, 63, 1541. 'Recommendations for nomenclature and symbolism for mass spectroscopy (including an appendix of terms used in vacuum technology). (Recommendations 1991)' on page 1545 (https://doi.org/10.1351/pac199163101541)",
    "PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 980 (https://doi.org/10.1351/pac199668040957)",
    "Red Book, 3rd ed., p. 35"
  ],
  "url": "https://mlchart.com/terminology/chemistry/mass-number/"
}