March 7, 1951 - Death of William Draper Harkins, first to predict the existence of the neutron and to propose the basic principle of nuclear fusion

Although he is known for his contributions to surface and nuclear chemistry and for being one of the first environmental chemists, he also investigated atomic theory, in particular the structure of the atomic nucleus and aspects of nuclear radioactivity. Among his achievements are:

• Introduce concepts such as ‘packing defraction’, a measure of the energy involved in the association of protons and neutrons within the nucleus of an atom.
• Correctly predicted the existence of the neutron in 1920 (as a proton-electron complex) and was the first to use the word ‘neutron’ about the atomic nucleus (the neutron was detected experimentally by James Chadwick in 1932).
• He predicted the existence of heavy hydrogen (or deuterium)
• He was the first to propose the basic principle of nuclear fusion in 1915, four years before Jean Baptiste Perrin published his theory in 1919-1920. Using Albert Einstein's concept of the equivalence of mass and energy, he showed that by combining four hydrogen atoms to produce one helium atom, a small amount of mass would be converted into energy; he correctly theorised that this process was a source of sterlar energy.
• In the early 1930s, he contributed to the second cyclotron with fellow University of Chicago scientist Robert James Moon, greatly improving its design. Experiments with Moon analysing the fusion processes between hydrogen and helium led him to conclude, correctly, that the fusion of hydrogen atoms and the subsequent production of helium was the energy-generating mechanism in the Sun and stars.
• He developed one of the first cosmological models that attempts to explain the abundance in the universe of each of the chemical elements in the periodic table, i.e. he made one of the first attempts to calculate the proportions of the elements in the universe.

If you want to know more about this scientist, click on the following link: William Draper Harkins