ニホニウム (Nh) は、安定同位体を持たないため標準原子量は定められない。
一覧 同位体核種Z（p）N（n）同位体質量（u）半減期核スピン数励起エネルギー278Nh1131650.344ms282Nh113169 73ms283Nh113170283.17645（78）#100（+490-45）ms284Nh113171284.17808（86）#0.48（+58-17）s285Nh113172285.17873（105）#2#min286Nh113173286.18048（101）#5#min287Nh113174287.18105（90）#20#min
参考文献 Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729（2003）. Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page. Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties, Nuc. Phys. A 729, pp. 3-128（2003）. National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database（retrieved Sept. 2005）. David R. Lide（ed.）, Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition, online version. CRC Press. Boca Raton, Florida（2005）. Section 11, Table of the Isotopes.