discovery of neutrons

¶ … Chadwick Learned to Love the Neutron

Chadwick was a student of eminent Kiwi (New Zealander) physicist Ernest Rutherford at Manchester University, England.

Absorbed cutting-edge physics from Rutherford, Geiger and Marsden, especially information related to the following:

the scattering of alpha particles from radium, which Rutherford used to deduce the existence of atomic nucleus (Oliphant, 1982).

" the atomic mass number A of nuclei is a bit more than twice the atomic number Z. For most atoms and that essentially all the mass of the atom is concentrated in the relatively tiny nucleus," (Nave, n.d.).

"the fundamental particles were protons and electrons, but that required that somehow a number of electrons were bound in the nucleus to partially cancel the charge of A protons," (Nave, n.d.).

C. Motivated to find out why there was a "disparity between an element's atomic number…and its atomic mass, which was usually in excess of the mass of the known protons present (Colwell, 2012).

II. The Experiments: The Bombardment of Beryillium

A. When beryillium is bombarded by alpha particles (such as those coming from radium or polynium), a stream of radiation is emitted, which is not electromagnetic or gamma radiation

B. Chadwick deduced that this radiation resulting from the bombardment of alpha particles consisted of a wave of uncharged particles "each of mass about the same as a proton" (Breithaupt, 2000, p. 589).

C. Chadwick hypothesized that this radiation was comprised of the elusive neutron, then conducted a series of experiments to prove it.

D. The experiments included those using cloud chambers, ionisation counters, and Geiger tubes. Wax was initially used as an experimental substance to test for the propulsion speeds of the presumed neutron radiation.

III. The Discovery

A. It only took Chadwick one month to discover the conclusive evidence that the neutron did indeed exist; the journal Nature published the report in 1932.

B. Chadwick described a neutron as " a highly penetrating neutral particle with a mass similar to the proton," ("The Neutron: Chadwick 1932," n.d.)

C. Chadwick explained the phenomenon in terms of snooker balls, noting that when the alpha particles from a radioactive source hit a nuclei, a proton is knocked free leaving behind a particle -- suggesting that the neutron is the same mass -- just as when a snooker ball is hit by a ball of the same mass it remains stationary.

IV. The Aftermath

A. Chadwick earned the Nobel Prize for his work.

B. Unfortunately, the work from Chadwick's discovery would be harnessed for great evil, causing Chadwick considerable consternation

1. He disparaged the way science was headed toward harnessing discoveries like his for military purposes.

2. He especially feared the American control of science (Oliphant, 1982).

C. Chadwick's discovery led to a "revolution in warfare," a "new source of energy," and "fundamental changes" to the study of science (Oliphant, 1982).