» 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've the same neutron number N. 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. Isotones have a different number of protons This is to be contrasted with Isotopes are nuclides having the same number of protons (Carbon-12 and Carbon-13) Isobars are nuc… (More on Isotone)