Two nuclides are isotones if they have the same neutron number N , but different proton number Z. For example, boron and carbon nuclei both contain 7 neutrons , and so are isotones.
Similarly, 36 S, 37 Cl, 38 Ar, 39 K, and 40 Ca nuclei are all isotones of 20 because they all contain 20 neutrons. Despite its similarity to the Greek for "same stretching", the term was formed by the German physicist K. Guggenheimer  by changing the "p" in " isotope " from "p" for "proton" to "n" for "neutron".
Neutron numbers for which there are no stable isotones are 19, 21, 35, 39, 45, 61, 89, , , and or more. In contrast, the proton numbers for which there are no stable isotopes are 43 , 61 , and 83 or more. Odd neutron numbers for which there is a stable nuclide and a primordial radionuclide are 27 50 V , 65 Cd , 81 La , 85 Sm , and Lu.
Neutron numbers for which there are two primordial radionuclides are 88 Eu and Gd and Re and Pt. From Wikipedia, the free encyclopedia. This article possibly contains original research.
Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed. June Learn how and when to remove this template message. This article is about a concept in nuclear physics.
Uses of isotopes in Medicine
For biochemistry, see Isotonicity. For the mathematical meaning, see monotonic function. Models of the nucleus. Nuclides ' classification.
Nuclear stability. Radioactive decay. Nuclear fission. Capturing processes.
NUCLEI- ISOTOPES, ISOBARS, ISOTONES, ISOMERS AND ISODIAPHERS
High-energy processes. Nucleosynthesis and nuclear astrophysics.
High-energy nuclear physics. General Chemistry.