Win an All-Access Pass!
Become a new yearly Curie (Radium) or Roentgen (Gold) Radiopaedia Supporter during December and be in the running to win one of four 12-month All-Access Passes. Find out more.


Isobars are atomic species that have the same mass number (A), but a different atomic number (Z).

Isobars should not be confused with isotopes, which share the same atomic number, and therefore belong to the same chemical element, but have varying mass numbers.

Examples of isobars include 14,6C; 14,7N; 14,8O. These atoms all have the same number of nucleons (14).

In nuclear physics, isobars tend to undergo beta decay.

A mnemonic that can be used to differentiate isotones from isotopes and isobars is as follows:

  • Same Z (number of protons) = isotopes
  • Same A (number of nucleons) = isobars
  • Same N (number of neutrons) = isotones
Imaging technology

Article information

rID: 79799
Synonyms or Alternate Spellings:
  • Isobars

ADVERTISEMENT: Supporters see fewer/no ads

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.