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Chemistry - James Chadwick and the neutron

James Chadwick and the neutron

Mass spectroscopy made it possible to determine relative mass. It was
accepted that atoms could have different masses and yet still be atoms of
the same element, i.e. isotopes.

The mystery of how atoms of the element could have masses, however still
had to be solved.

Carbon atoms (six protons) were expected to have six times the mass of
hydrogen atoms (one proton). This is assuming, of course, that electrons,
with mass approximately one-two thousandth the mass of a proton, make an
insignificant contribution to the overall mass of an atom.

But, the most common carbon atom was shown to have 12 times the mass of
the most common hydrogen atom.

In 1932, James Chadwick proposed the existence of more particles in the
nucleus of atoms; particles that had the same mass as a proton but carried
These particles were called neutrons, from the expression neutral proton.

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