同中子素（英语：Isotone），其定义是两个不同质子数的核种，具有相同的中子数。例如：N与O都具有8个中子。此词汇是由德国物理学家K.古根海玛所创，是将英文同位素（英语：Isotope）中的「p」置换成代表中子的「n（neutron）」。

周期表的稳定核种中，有7种同中子素共具最高82个中子，其次是有5种同中子素具50个中子与20个中子。中子为魔数的同中子素，其稳定核种较多。

S、Cl、Ar、K、Ca

Kr、Sr、Y、Zr、Mo

Xe、Ba、La、Ce、Pr、Nd、Sm

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

Two nuclides are isotones if they have the very same neutron number N, but different proton number Z. For example, boron-12 and carbon-13 nuclei both contain 7 neutrons, and so are isotones . Similarly, S, Cl, Ar, K, and 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 replacing the "p" in "isotope" with "n" for "neutron".