Atomic Theory Handout CNS 8

Atomic Theory Handout
CNS 8
Read the following information about atomic theory. Underline or highlight the
important information in each paragraph. Write notes/questions in the margins to
help in your understanding of this material.
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John Dalton
1766 – 1844
John Dalton pictured the
atom as a hard sphere with
the same makeup throughout
the entire atom.
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William Crookes
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1832 – 1919
J J Thomson
1856 - 1940
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Ernest Rutherford
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Erwin Schrödinger 1887- 1961
Erwin Schrodinger was an Austrian theoretical physicist who was
one of the fathers of quantum mechanics, and is famed for a number of
important contributions to physics, especially the Schrödinger
equation, for which he received the Nobel Prize in Physics in 1933. In
1935, after extensive correspondence with personal friend Albert
Einstein, he proposed the Schrödinger's cat thought experiment. It
came as a result of his dissatisfaction with the quantum condition in
Bohr's orbit theory and his belief that atomic spectra should really be
determined by some kind of eigenvalue problem. For this work he
shared with Dirac the Nobel Prize for 1933.
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James Chadwick
1891-1974
James Chadwick was born in England, on 20th
October, 1891. During World War I, he was interned in
the Zivilgefangenenlager, Ruhleben. After the war, in
1919, he returned to England to accept the Wollaston
Studentship at Cambridge, and to resume work under
Rutherford.
In 1932, Chadwick made a fundamental discovery
by proving the existence of neutrons - elementary particles devoid of
any electrical charge. Chadwick prepared the way towards the fission
of uranium 235 and towards the creation of the atomic bomb. For this
epoch-making discovery he was awarded the Hughes Medal of the Royal
Society in 1932, and subsequently the Nobel Prize for Physics in 1935.
Sir James Chadwick died on July 24, 1974.
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Niels Bohr
1885 - 1962
Niels Bohr was born and educated in Copenhagen, Denmark. He lived, worked, and
died there, too. But his mark on science and history was worldwide. His work and
personal convictions were part of the larger stories of the century.
At the University of Copenhagen, he studied physics and played soccer (though not
as well as his brother, who helped the 1908 Danish soccer team win an Olympic
silver medal). After receiving his doctorate in 1911, Bohr traveled to England on a
study grant and worked under J.J. Thomson, who had discovered the electron 15
years earlier.
Bohr began to work on the problem of the atom's structure. Ernest Rutherford
had recently suggested the atom had a miniature, dense nucleus surrounded by a
cloud of nearly weightless electrons. There were a few problems with the model,
however. For example, according to classical physics, the electrons orbiting the
nucleus should lose energy until they spiral down into the center, collapsing the
atom. Bohr proposed adding to the model the new idea of quanta put forth by Max
Planck in 1901. That way, electrons existed at set levels of energy, that is, at fixed
distances from the nucleus. If the atom absorbed energy, the electron jumped to a
level further from the nucleus; if it radiated energy, it fell to a level closer to the
nucleus. His model was a huge leap forward in making theory fit the experimental
evidence that other physicists had found over the years. A few inaccuracies
remained to be ironed out by others over the next few years, but his essential idea
was proved correct. He received the Nobel Prize for this work in 1922, and it's
what he's most famous for. But he was only 37 at the time, and he didn't stop
there. Among other things, he put forth the theory of the nucleus as a liquid drop,
and the idea of "complementarity" -- that things may have a dual nature (as the
electron is both particle and wave) but we can only experience one aspect at a time.
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Atomic Energy
Atomic energy is energy produced by atoms.
 Nuclear energy, the energy resulting of
potential difference of the nuclear force
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Nuclear reaction, a process in which two nuclei or nuclear
particles collide, to produce different products than the initial
products; see also nuclear fission and nuclear fusion. Nuclear
reactions are used to produce electrical energy by nuclear
reactors
Radioactive decay, the set of various processes by which unstable
atomic nuclei (nuclides) emit subatomic particles
The energy of inter-atomic or chemical bonds, which holds atoms
together in compounds.
The term originated in 1903 when Ernest Rutherford began to speak of
the possibility of atomic energy. The term was popularized by H. G.
Wells in the phrase, "splitting the atom", devised at a time prior to the
discovery of the nucleus.
 The science of atomic radiation, atomic change and nuclear
fission was developed from 1895 to 1945, much of it in
the last six of those years.
 Over 1939-45, most development was focused on the
atomic bomb.
 From 1945 attention was given to harnessing this
energy in a controlled fashion for naval propulsion and
for making electricity.
 Since 1956 the prime focus has been on the
technological evolution of reliable nuclear power plants.
 Uranium was discovered in 1789 by Martin Klaproth, a
German chemist, and named after the planet Uranus.
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