Atomic Structure-Continue
The Discovery of the Neutron
By 1926, the year that Schrodinger proposed the electron cloud model of the atom, scientists had made a big leap forward in understanding the atomic structure. They were already aware that atoms consisted of at least two different types of particles—negatively charged electrons and positively charged protons. But there remained one more discovery that would complete the picture of the atom.
Rutherford continued his experimental work, bombarding substances with high-energy particles, which provided a rich set of data about these substances. The data suggested that the mass of an atom’s nucleus is much larger than can be accounted for by the number of positively charged particles present in each nucleus. He became convinced that the nuclei (plural of “nucleus”) contained neutral particles having no charge, in addition to positively charged protons. He assigned his student James Chadwick to investigate.
Chadwick experimented with different elements, placing them in the path of high-energy particles. Chadwick was able to show that the nucleus contains, nucleus contains, in addition to protons, particles of about the name mass but carrying no charge. He published his results in 1932, naming neutrons as the neutral particles in the nucleus of an atom.
Before this result, scientists were only aware of one type of particle in an atom’s nucleus, the proton. Chadwick’s discovery showed that a nucleus contains protons and neutrons, known collectively as the nucleons of an atom.
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Chadwick’s discovery of
allowed scientists to understand what structures particles contributed to the mass of an atom.
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An atom is made of a very dense
at the center, made up of protons having a positive charge and neutrons having no charge.
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The two particles making up the nucleus are known collectively as
.
