Isotone

Part of speech: noun

Definitions

1. Nuclides that contain the same number of neutrons but differ in their number of protons, so they are different elements sharing a neutron count
2. Atoms or nuclei sharing an identical neutron total while having distinct atomic numbers and therefore belonging to separate chemical elements
3. Forms of different elements whose nuclei hold the same quantity of neutrons, distinguished from one another by their proton counts

Etymology: Kurt Guggenheimer, a German physicist, coined "isotone" in 1934, and the word was built by swapping a single letter. "Isotope" had already been in use for atoms of the same element with different masses, and its "p" was read as standing for "proton," the particle that defines an element's identity. Guggenheimer's new term kept the "iso-" prefix, which means "equal" in Greek, but replaced that letter with "n" for "neutron." The result describes nuclei that share the same number of neutrons while differing in their numbers of protons. Because the two words differ by only one letter, the pairing is easy to remember: isotopes share the element, and isotones share the neutron count.