# How is the nucleus of a uranium-238 atom different to the nucleus of a uranium-235 atom?

Jan 2, 2017

""^238U has 3 more neutrons than ""^235U, and...........
The isotopes differ in the number of neutrons contained in their nucleus. ""^238U contains $\left(238 - 92\right)$ neutrons; ""^235U contains $\left(235 - 92\right)$ neutrons.
I forget which isotope is the fissile one. It's ""^235U isn't it, and ""^238U is the fertile isotope? Anyway, this is the chemistry not the physics section.