Isotone

Two nuclides are isotones if they have the same number <math>N<math> of neutrons. This is to be contrasted with:

• Isotopes are nuclides having the same number of protons
• Isobars are nuclides having the same mass number, i.e. sum of protons plus neutrons; see isobar for the meaning as on a weather chart.
• Nuclear isomers are different excited states of the same type of nucleus. A transition from one isomer to another is accompanied by emission or absorption of a gamma ray, or the process of internal conversion. (Not to be confused with chemical isomers.)

The word "isotone" looks like Greek for "same stretching", but it actually is "isotope" with "p" for "proton" replaced by "n" for "neutron".