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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 pictured the atom as a hard sphere with the same makeup throughout the entire atom.

John Dalton

1766 – 1844

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William Crookes 1832 – 1919

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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

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.