Neutron number

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Element C
Isotope/Nuclide 14C
With atomic number 14
With neutron number 14

Nuclides that have the same neutron number but a different proton number are called isotones. This word was formed by replacing the p in isotope with n for neutron. Nuclides that have the same mass number are called isobars. Nuclides that have the same neutron excess are called isodiaphers.[1]


Neutron number is primarily of interest for nuclear properties. For example, actinides with odd neutron number are usually fissile (fissionable with slow neutrons) while actinides with even neutron number are usually not fissile (but are fissionable with fast neutrons).

Only 57 stable nuclides have an odd neutron number, compared to 200 with an even neutron number. No odd-neutron-number isotope is the most naturally abundant isotope in its element, except for beryllium-9 which is the only stable beryllium isotope, nitrogen-14, and platinum-195.



  1. ^ Teh Fu Yen, Chemistry for Engineers (Imperial College Press, 2008), p.265