English

Noun

isotone

1. either of a number of nuclides of different elements that have the same number of neutrons

See also

• isobar
• isotope

Related terms

• isotonic

This article is about a concept in nuclear physics. For biochemistry see isotonic. For the mathematical meaning, see monotone.

Two nuclides are isotones if they have the same number N of neutrons. For example, Boron-12 and Carbon-13 both have 7 Neutrons; S-36, Cl-37, Ar-38, K-39, Ca-40, these nuclei contain 20 neutrons each etc.

This is to be contrasted with

• Isotopes are nuclides having the same number of protons (Carbon-12 and Carbon-13)
• Isobars are nuclides having the same mass number; i.e. sum of protons plus neutrons; Carbon-12 and Boron-12. See Isobar (Contour line) for the meaning in the context of weather charts.
• 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".