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When talking about Rutherford being the first to split the atom (1919), where he bombarded nitrogen gas with alpha particles to produce oxygen and a proton, I always use those words or merely state that he was the world's first successful alchemist. I have never used the word "fission". However, in paraphrasing me the authors aren't wrong. It is just a matter of semantics.  The word "fission" is from the Latin "fissio" as in "fissure", a crack. Biologists took up this word to cover cell division. In their case it was one cell dividing into two equal cells the same as the one it started with. Physicists then used this word to describe an atomic nucleus dividing into two different but nearly equal parts as in the case of uranium bombarded with a neutron.

This is merely all part of the evolution of the English language. Note that Latin usage was just to crack (no equal parts essential), biology usage was to divide into two identical cells with no shrapnel, and physics usage to divide into two un-identical objects, each about half the mass of the original, plus some shrapnel. (eg neutrons), which produced a chain reaction.  

In having to have thought this through as above for the first time in order to address this usage, I would be happy to say that Rutherford was the first to produce a fission reaction. If not through alphas and nitrogen (producing not identical objects), then through his instructions to Cockcroft and Walton to build a proton accelerator and fire a "p" into "7Li" to give out only two, identical, objects (alphas, and no shrapnel).   Perhaps we have Rutherford for fission in the Latin sense (alpha plus nitrogen), also for the biological sense (p + 7Li) but none of them for the true biological sense whereby one object by itself divides into two identical objects.

It should not be forgotten that Rutherford was also the first to suggest (1920) [1] that a neutral particle (neutron), of similar mass to that of a proton, had to exist to explain isotopes. At the same time he suggested that, being uncharged, the neutron could more easily penetrate into an atomic nucleus. Uranium "fission" was one of the few discoveries that escaped him.

It is likely an historian of nuclear fission could tell us all when the word "fission" was first used in conjunction with nuclear reactions. It doesn't appear to be in Rutherford's lifetime, during which newspaper headlines mentioned "transmutation", "alchemy", "splitting the atom", and "turning lead into gold." He died before uranium “fission”, generally accepted today as the neutron chain reaction in uranium, was discovered.

I had addressed several of these points earlier in www.rutherford.org.nz – Miscellaneous – Mythology – Splitting the Atom.

Dr John Campbell,
Physics Department, University of Canterbury, New Zealand.
Author of "Rutherford Scientist Supreme" and www.rutherford.org.nz

1.  E. Rutherford, “Nuclear Constitution of Atoms” (Bakerian Lecture),  Proc. Roy. Soc., A97: 374-400 (1920).