Atomic Theory
When looking at the
History of the Atom.
The Atom was always
Neutral.
Let’s Take a Trip Through Time!
Democritus
460 – 370 B.C.
• Greek Philosopher
• There are various basic
elements from which all matter
is made
• Coined the term “atom” which
means indivisible
• Everything is composed of
small atoms moving in a void
• Some atoms are round, pointy,
oily, have hooks, etc. to
account for their properties
• Ideas rejected by leading
philosophers because void =
no existence
“Atomos” = “indivisible”
“The material cause of all things that exist
is the coming together of atoms and void.
Atoms are too small to be perceived by
the senses. They are eternal and have
many different shapes, and they can
cluster together … By aggregation they
provide bulky objects that we can
perceive with our sight and other
senses… There is no void in atoms, so
they cannot be divided.”
Demokritos c. 460-370 BC
First Concept of an Atom
Antoine Lavoisier
1743-1794
• French
• Known as the “Father of
Modern Chemistry”
• Came up with Law of
Conservation of Mass
• He had discovered that
mass is conserved within
a chemical reaction. The
mass of the products of a
chemical reaction is
always the same as the
mass you started with.
John Dalton
1766-1844
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Born in England
Introduced his ideas in 1803
Proposed the “Atomic Theory”
– Each element is composed of
extremely small particles called
atoms
– All the atoms of a given element are
identical, but they differ from those
of any other element
– Atoms of different elements have
different properties including
different masses
– Compounds are formed when
atoms of more than one kind of
•
atom combine
Taught at University of Manchester,
was said to “see things differently
than others”
Dalton’s Model
The Cannonball Model
Michael Faraday
1791-1867
• Born in England
• Coined term “electrolysis”
–used electricity on
solutions to split water
(1832)
• Also moved a wire
through a magnet to
create an electrical
current which lead to
invention of generators
(Industrial Revolution)
James Clerk Maxwell
1831-1879
• Developed the
Maxwell-Boltzmann
kinetic theory of
gases (1866). This
theory showed that
temperatures and
heat involved only
molecular movement.
• Electromagnetic
Fields
Dmitri Mendeleev
1834-1907
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Russian
Developed the Periodic Table
(1869)
His first Periodic Table was
compiled on the basis of arranging
the elements in ascending order of
atomic weight and grouping them
by similarity of properties.
Left space for new elements, and
predicted three yet-to-bediscovered elements including
eke-silicon and eke-boron.
His table did not include any of the
Noble Gases, however, which had
not yet been discovered.
Henri Becquerel
1852-1908
• Discovery of Radioactivity
(1896)
• Coined the term “X-Ray”
• For his discovery of
spontaneous radioactivity
Becquerel was awarded
half of the Nobel Prize for
Physics in 1903, the other
half being given to Pierre
and Marie Curie for their
study of the Becquerel
radiation
J.J. Thomson
1856-1940
• Discovered electron
1897 – Cathode Ray
Experiment
• Plum Pudding model
1904
– Electrons in a soup of
positive charges
• Discovered isotopes 1913
• Noble Prize in Physics
(1906)
Plum Pudding Model
Marie Sklodowska Curie
1867-1934
• Born in , Warsaw, Poland
(November 7, 1867)
• Studied Uranium
• Discovered Radium and
Polonium
• She worked with radioactivity,
x-rays in medicine, and
changes in the atomic nucleus.
Curie’s discovery in changes in
the atomic nucleus led the way
toward the modern
understanding of the atom as
an entity that can be split to
release enormous amounts of
energy.
Marie Curie (con’t)
• Awarded Noble Prize in Physics (with H. Becquerel and
Pierre Curie) in 1903. “in recognition of the extraordinary
services they have rendered by their joint researches on
the radiation phenomena discovered by Professor Henri
Becquerel."
• Awarded Noble Prize in Chemistry in 1911. "in
recognition of her services to the advancement of
chemistry by the discovery of the elements radium and
polonium, by the isolation of radium and the study of the
nature and compounds of this remarkable element."
Albert Einstein
1879 - 1955
• Jew born in Germany
• Developed the Theory of
Relativity and specifically
mass-energy
equivalence, E = mc 2
• Received the 1921 Nobel
Prize in Physics "for his
services to Theoretical
Physics, and especially
for his discovery of the
law of the Photoelectric
Effect.
Albert Einstein
• Became a United States Citizen in 1940
• With Leo Szilard wrote a letter to then President
FDR on Aug 2, 1939 that lead to the Manhattan
Project. (Einstein did not help develop the
Atomic Bomb other than to sign the letter)
• Manhattan Project-brought together top
scientists from the US, Britain, Canada and
refugees of Nazi Germany to develop Nuclear
Weapons
Robert Millikan
1868-1953
• Born in Morrison, Illinois
• “Oil Drop Experiment” (1909)
Determined the charge and
mass of an electron
• Set out to determine the
measurement of electrical
charge with the use of x-rays.
In the process of doing so he
discovered the most
persuasive evidence to
support that electrons were
basic particles, and that they
all had the equal mass and
charge.
Ernest Rutherford
1871-1937
• Born in New Zealand
• Nuclear Model 1910
– Gold Foil Experiment
• Atom is mostly empty
space
• Nucleus has a positive
charge
• Noble Prize in Chemistry
(1908) “for his investigation into
the disintegration of the elements,
and the chemistry of radioactive
substances”
Ernest Rutherford
1871-1937
doctoral student of
Thomson 1895-1989
Physics Chair at McGill from
1898-1907 before returning
to England and teaching at
Manchester University
takes over Cavendish Chair
of Physics from Thomson in
1919
Alpha Particle Experiment
Show the Gold Foil Experiment Animation
Rutherford Model
Nuclear Model
H. G. J. Moseley
1887 - 1915
• English Physicist
• Using x-ray tubes, determined
the charges on the nuclei of
most atoms.
• He wrote “The atomic number
of an element is equal to the
number of protons in the
nucleus”.
• This work was used to
reorganize the periodic table
based upon atomic number
instead of atomic mass. (1913)
Niels Bohr
1885-1962
• Danish
• Planetary Model 1913
– Nucleus surrounded by
orbiting electrons at
different energy levels
– Electrons have definite
orbits
• Utilized Planck’s
Quantum Energy theory
• Worked on the Manhattan
Project (US atomic bomb)
Bohr’s Model
Quantum Energy Levels
-Atomic Model has
electrons found in
specific energy levels.
Bohr Model for Nitrogen
Prince Louis-Victor deBroglie
1892-1987
• educated and worked in
France - BA in 1913 &
graduate work after
serving for France in WWI
• his 1924 doctoral thesis
introduced “wave
mechanics” - the idea that
the electron could be
treated as a wave
• 1929 Nobel Prize in
Physics
Werner Heisenberg 19011976
• Born in Wurzburg, Germany
• 1923 PhD in Munich
• 1924-’25 works with Bohr in
Copenhagen
• establishes “quantum mechanics”
when only 23 years old in 1925 includes Uncertainty Principle
• 1932 Nobel Prize in Physics
• 1941 director of Kaiser Wilhelm
Institute in Berlin - captured by US
troops at end of WWII & sent to
England; returns to Germany after
the war
Erwin Schrødinger 18871961
• Born and educated in Vienna;
serves in Austrian Army in WWI
• 1926 publishes “wave
equation” model of electrons
• Goes to Germany in 1927 but
leaves in 1933 with rise of Nazis;
ends up in Austria in 1937;
recants opposition to Nazis but is
harassed and escapes in 1938
• 1933 Nobel Prize in Physics with
Dirac
• 1940 establishes Institute for
Advanced Studies in Dublin
Ernst Schrödinger 1887-1961
Werner Heisenberg 1901-1976
• Quantum Mechanical Model or
the Wave Mechanical Model or
the Cloud Model 1926
The accepted way we presently
look at the atom
– Electrons found in a region
(cloud) around the nucleus
– Electrons are in probability
zones called “orbitals”, not
orbits and the location
cannot be pinpointed
– Electrons are particles and
waves at the same time
– Developed quantum
numbers based on theories
of Einstein and Planck
Wave – Mechanical Model
James Chadwick
1891-1974
• Born in England
• Made the important
discovery of neutrons
(1932). A particle in an
atom that held a neutral
charge, neither positive
nor negative. This
discovery helped tell the
difference between the
atomic number and the
mass number.
• Was awarded the Nobel
Prize in Physics in 1935
• A student of Rutherford
Otto Hahn 1879 – 1968
Fritz Strassmann 1902 - 1980
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Worked with Lise Meitner in
Berlin, until Meitner was forced to
flee Nazi Germany
Experimented by bombarding
uranium’s heavy nuclei with
neutrons- got unexpected results
– lighter elements, such as
barium, were produced.
• Hahn is regarded as "the
father of nuclear chemistry"
and the "founder of the atomic
age".
Lise Meitner 1878 – 1968
Otto Robert Frisch 1904 - 1979
• Meitner, a physicist, worked for
years with chemists Hahn and
Strassmann to study the
behavior of nuclei
• Meitner, working with her
nephew, Frisch, were the first
to understand that uranium
nuclei could be split when
bombarded by neutrons.
• Calculated the amount of
energy released each time a
uranium nucleus undergoes
fission (an example of E = mc
squared at work)
Glenn Seaborg
1912 -1999
• American born in Ishpeming,
Michigan
• Through the years of 1937 to
1939 he published many
scientific papers. He also
discovered 10 atomic elements
and one was even named after
him, "seaborgium."
• Noble Prize in Chemistry
(1951) w/ Edwin McMillan “for
their discovery in the chemistry
of the transuranium elements”
• Suggested a change in the
layout of the Periodic Table
Glenn Seaborg (con’t)
•
Appointed Chancellor of the University of California at Berkeley in 1958
– Named Marv Levy as the Head Football Coach in 1960 (a position he held
until1963)
"In 1944, Seaborg formulated the 'actinide concept' of heavy element electronic
structure which predicted that the actinides – including the first eleven
transuranium elements – would form a transition series analogous to the rare
earth series of lanthanide elements. Called one of the most significant changes
in the periodic table since Mendeleev's 19th century design, the actinide concept
showed how the transuranium elements fit into the periodic table."
Headed the plutonium work of the Manhattan Project (1942-1946)
Co-discoverer of plutonium and all further transuranium elements through element
102
Between 1961 and 1971, Seaborg was the chairman of the AEC, a predecessor
agency of the Department of Energy (DOE). Seaborg was active in national
service, advising ten presidents from Franklin D. Roosevelt through George H.
W. Bush.
Enrico Fermi
1901 - 1954
• Italian
• Used neutron to split the
nucleus of uranium atom
(First controlled chain
reaction)
• Fled Italy in 1938 and
became a naturalized
American
• Lead Manhattan Project
at University of Chicago
Manhattan Project
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Started because F.D.R was
persuaded by Einstein and other
scientist after Hilter’s assault on
Poland
Brought together the top scientists
from US., England, Canada, and
refugees of Nazi Germany
Under the leadership of Enrico
Fermi, took place at the University
of Chicago’s Stagg Field (Football
Field)
On July 16, 1945 in a desert near
Alamogordo, New Mexico experts
detonated the first atomic device.
World War II
•
December 7, 1941
Pearl Harbor
• Potsdam Conference, held in
Berlin in July 1945
President Truman with J.
Stalin issue a ultimatum to Japan,
surrender or be destroyed
• August 6, 1945
Dropped bomb on Hiroshima
• August 9, 1945
Dropped bomb on
Nagasaki
• August 10, 1945
Japan Surrendered
Review of Atomic Models
1803 – Dalton
Cannonball Model
1897 – Thomson
Plum pudding Model
1909 – Rutherford
Nuclear Model
1913 – Bohr
Planetary Model
Present
Wave – Mechanical Model