Possible Existence of a Neutron" in Nature Vol. 129, January to June, 1932 [CHADWICK ASSERTS "POSSIBLE" EXISTENCE OF A NEUTRON. BOUND FULL VOLUME 1st EDITION]

London: Macmillan, 1932. 1st Edition. FULL VOLUME 1st EDITION of James Chadwick's initial speculation about the "possible" existence of the neutron, a subatomic particle with no electrical charge and a mass slightly larger than that of a proton. When, three months later, Chadwick affirmed his discovery, his assertion rewrote then current beliefs in nuclear science: he had proven that elementary particles devoid of any electrical charge existed. "For the discovery of the neutron," Chadwick was awarded the 1935 Nobel Prize in Physics (Nobel Prize Committee).

"The discovery of the neutron made by Chadwick led to a much deeper understanding of the nature of matter, explaining for example why isotopes of elements exist. It also inspired Enrico Fermi and other physicists to investigate nuclear reactions produced by neutrons, leading to the discovery of nuclear fission" (Hutchinson, Dictionary of Scientific Biography, I, 227). This discovery provided a new tool for inducing atomic disintegration, since neutrons, being electrically uncharged, could penetrate undeflected into the atomic nucleus.

"In contrast with the helium nuclei (alpha rays) which are charged, and therefore repelled by the considerable electrical forces present in the nuclei of heavy atoms, this new tool in atomic disintegration need not overcome any electric barrier and is capable of penetrating and splitting the nuclei of even the heaviest elements. Chadwick in this way prepared the way towards the fission of uranium 235 and towards the creation of the atomic bomb.

Prior to Chadwick's discovery and until 1932, the atom was known to consist of a positively charged nucleus surrounded by enough negatively charged electrons to make the atom electrically neutral. Most of the atom was empty space, with its mass concentrated in a tiny nucleus.

Chadwick knew that in "experiments in which beryllium was bombarded by alpha particles, a usually energetic gamma radiation appeared to be emitted. It was more penetrating than gamma radiation from radioactive elements. Measurements of the energies involved and the conservation of energy and momentum suggested to Chadwick that a new kind of particle was being produced rather than radiation.

"The results pointed towards a neutral particle made up of a proton and an electron. Its mass should thus be slightly greater than that of the proton. Because the mass of the beryllium nucleus had not then been measured, Chadwick designed and carried out an experiment in which boron was bombarded with alpha particles. This produced neutrons, and from the mass of the boron nucleus and other elements and the energies involved, Chadwick determined the mass of the neutron to be 1.0067 atomic mass units, slightly greater than that of the proton" (ibid).

NOTE: We offer the later paper in which Chadwick affirms his speculation about the "possible" existence of the neutron" separately. That paper is titled "Existence of a Neutron" and was published in the same journal later in 1932. CONDITION & DETAILS: London: Macmillan. Complete volume. 4to (Quarto). 10.5 x 7.5 inches (262 x 187mm). [lx], 952, [4]. Ex-libris bearing a pictorial bookplate on the front paste down, a small stamp and blind stamp on the title page; small unobtrusive darkened square area at the foot of the spine showing where a spine label has been removed. Bound in green cloth, gilt-lettered at the spine. Very tightly bound; minor rubbing at the edges and spine. Bright and clean throughout.