History of the Atom

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History of the Atom

• Scientists and Their Contribution to the Model of
  an Atom

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History of the Atom - Timeline
Antoine Lavoisier makes a substantial number of
contributions to the field of Chemistry
J.J. Thomson discovers the electron and proposes
the Plum Pudding Model in 1897
Niels Bohr proposes the Bohr Model in 1913
James Chadwick discovered the neutron in in 1932
1766 1844
1871 1937
1887 1961
460 370 BC
1700s
1800s
1900s
Erwin Schrodinger describes the electron cloud in
1926
Democritus proposes the 1st atomic theory
John Dalton proposes his atomic theory in 1803
Ernest Rutherford performs the Gold Foil
Experiment in 1909
1891 1974
1743 1794
1885 1962
1856 1940
Click on picture for more information
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Democritus(460 BC 370 BC)

• Proposed an Atomic Theory (Atomos or Atomon)
  (along with his mentor Leucippus) which states
• all atoms are small, hard, indivisible and
  indestructible particles made of a single
  material
• Can be rearranged to form different shapes and
  sizes.
• Aristotle did not support his atomic theory

Image taken from https//reich-chemistry.wikispac
es.com/T.GlennTimeLineProject
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Antoine Lavoisier (1743 1794)

• Known as the Father of Modern Chemistry
• Was the first person to generate a list of
  thirty-three elements in his textbook
• Discovered / proposed that combustion occurs when
  oxygen combines with other elements
• Discovered / proposed the Law of Conservation of
  Mass (or Matter) which states, in a chemical
  reaction, matter is neither created nor destroyed
• Devised the metric system
• Was married to a 13-year old Marie-Anne Pierette
  Paulze she assisted him with much of his work
• Was a tax-collector that was consequently
  guillotined during the French Revolution

Image taken from www.ldeo.columbia.edu/.../v1001/
geotime2.html
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John Dalton (1766 1844)

• In 1803, proposed an Atomic Theory which states
• All substances are made of atoms atoms are small
  particles that cannot be created, divided, or
  destroyed.
• Atoms of the same element are exactly alike, and
  atoms of different elements are different
• Atoms join with other atoms to make new
  substances
• Calculated the atomic weights of many various
  elements
• Was a teacher at a very young age
• Was color blind

Image taken from chemistry.about.com/.../John-Dal
ton.htm
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J.J. Thomson (1856 1940)

• Proved that an atom can be divided into smaller
  parts
• While experimenting with cathode-ray tubes,
  discovered corpuscles, which were later called
  electrons
• Stated that the atom is neutral
• In 1897, proposed the Plum Pudding Model which
  states that atoms mostly consist of positively
  charged material with negatively charged
  particles (electrons) located throughout the
  positive material
• Won a Nobel Prize, 1906

Image taken from www.wired.com/.../news/2008/04/d
ayintech_0430
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Ernest Rutherford (1871 1937)

• In 1909, performed the Gold Foil Experiment and
  suggested the following characteristics of the
  atom
• An atom consists of a small core, or nucleus,
  that contains most of the mass of the atom
• This nucleus is made up of particles called
  protons, which have a positive charge
• The protons are surrounded by negatively charged
  electrons, but most of the atom is actually empty
  space
• Rutherfords model was called the planetary
  model
• Did extensive work on radioactivity (alpha
  beta particles, gamma rays/waves) and was
  referred to as the Father of Nuclear Physics
• Won a Nobel Prize, 1908
• Was a student of J.J. Thomson
• Was on the New Zealand 100 bill

Image taken from http//www.scientific-web.com/en
/Physics/Biographies/ErnestRutherford.html
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Marie Curie
Marie Curie(1867 1934)

• Pioneered the science of radiology study of
  radioactive decay
• Developed methods for the separation of radium
  from its ore
• Promoted use of radium to alleviate soldiers
  suffering
• referred to as the Mother of Modern Physics
• Won a Nobel Prize, 1903
• Discovered the element Polonium

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Lise Meitner(1878 1968)

• Collaborated with Otto Hahn in the study of
  chemistry, Hahn won Nobel Prize for their work
• Einstein referred to her as the German Marie
  Curie
• In 1939, co-discovered (with Hahn) nuclear
  fission, proving the atom could be broken down
  into sub-atomic particles

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Niels Bohr (1885 1962)

• In 1913, proposed the Bohr Model, which suggests
  that
• electrons travel around the nucleus of an atom in
  orbits or definite paths.
• electrons can jump from a path in one level to a
  path in another level (depending on their energy)
• Won a Nobel Prize, 1922
• Worked with Ernest Rutherford

Image taken from commons.wikimedia.org/wiki/File
Niels_Bohr.jpg
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Louis de Broglie(1892-1987)

• In 1924, presented research that led to the
  development the theory of Wave Mechanics also
  called Quantum Theory or Quantum Mechanics
• transformed knowledge of physical phenomena on
  the atomic scale.
• Won Nobel Prize, 1929

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Werner Heisenberg(1901-1976)

• Studied plasma physics, atomic physics and
  thermonuclear processes
• Won Nobel prize, 1932
• Famous for Heisenberg Uncertainty Principle
  electrons do NOT travel in neat orbits
• 1925-Introduced Theory of Quantum Mechanics to
  explain behaviors of electrons and other
  subatomic particles

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Erwin Schrodinger (1887-1961)

• In 1926, he further explained the nature of
  electrons in an atom by stating that
• the exact location of an electron cannot be
  stated therefore, it is more accurate to view
  the electrons in regions called electron clouds
  electron clouds are places where the electrons
  are likely to be found
• Did extensive work on the Wave formula ?
  Schrodinger equation
• Won a Nobel Prize, 1933

Image taken from nobelprize.org/.../1933/schrodin
ger-bio.html
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James Chadwick (1891 1974)

• Realized that the atomic mass of most elements
  was double the number of protons ? discovery of
  the neutron in 1932
• Worked on the Manhattan Project
• Worked with Ernest Rutherford
• Won a Nobel Prize, 1935

Image taken from www.wired.com/.../news/2009/02/d
ayintech_0227
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Murray Gell-Mann(1929 )

• Won the Nobel Prize, 1969
• In 1964 proposed that protons and neutrons were
  made up of sub-subatomic particles called
  quarks
• Can never be isolated
• There are up quarks and down quarks

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Progression of the Atomic Model
The structure of an atom, according to
Democritus John Dalton
J.J. Thomson
Ernest Rutherford
Neils Bohr
Erwin Schrodinger
James Chadwick