Joseph John Thomson

1
Joseph John Thomson

• Plum Pudding model of the atom
• Atom is composed of negatively and positively
  charges particles
• Used the Crookes tube
• electrons are particles
• determined the ratio of charge to mass for the
  electron
• qe/m 1.7 x1011 C/Kg
• Nobel Prize in Physics - 1906

2
Henri Bequerel

• Discovered that uranium spontaneously produced a
  type of radiation that could fog photographic
  sheets
• Wrapped uranium salts in black paper and placed
  them on top of photographic plates
• Nobel Prize in Physics - 1903
• "in recognition of the extraordinary services he
  has rendered by his discovery of spontaneous
  radioactivity"

3
Marie Curie (Pierre Curie)

• After Becquerels discovery of radiation being
  emitted from uranium, discovered that pitchblende
  (an ore of uranium) emitted more radiation than
  pure uranium
• Isolated two new elements polonium and radium
  (900 times more radioactive than uranium) from
  over two tons of pitchblende ore.
• Marie Curies research notebooks are held in lead
  lined casks in Paris - still highly radioactive
• Nobel Prize in Physics - 1903
• "in recognition of the extraordinary services
  they have rendered by their joint researches on
  the radiation phenomena discovered by Professor
  Henri Becquerel"
• Nobel Prize in Chemistry - 1911 (Marie Curie
  alone)
• "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"

4
Ernst Rutherford

• Gold Foil experiment
• a student of a students of his shot beams of ?
  particles at a very thin sheet of gold
• most went straight through but a few ? particles
  were deflected back at the beam
• Postulated that the atom was split into a nucleus
  with the greater part of the mass and that all of
  the positive charge was confined there
• Calculated the total charge of the nucleus for
  many different elements
• Nobel Prize in Chemistry - 1908
• "for his investigations into the disintegration
  of the elements, and the chemistry of radioactive
  substances"

5
H.G.J. Moseley

• Student of Rutherfords
• Provided experimental evidence that the periodic
  table should be arranged by anomic number not
  weight (1913)
• X-ray frequency emitted from 39 elements
  correlated with the atomic number, not the atomic
  weight
• Neutrons had not been discovered at this point!
• Killed in the trenches of WWI in 1915 at age 27

6
James Chadwick

• As researchers studied atomic disintegration,
  found that the atomic number was always less than
  the atomic mass
• Discovered the neutron
• non-charged particle in the nucleus with about
  0.1 more mass than a proton
• His discovery of neutrons led to the development
  of neutron beams that were seminal to the
  development of the nuclear bomb
• Nobel Prize in Physics - 1935
• "for the discovery of the neutron"

7
Robert Millikan

• Millikan Oil Drop experiment
• Established the charge on the electron to be
  1.602 x 10-19 C
• From this determined both mass and
• Exact value of Avogadros number
• Established charge is a discreet constant and not
  a statistical average
• Nobel Prize in Physics - 1923
• "for his work on the elementary charge of
  electricity and on the photoelectric effect"

8
Niels Bohr

• Developed the modern view of the structure of the
  atom
• 4 assumptions
• 1) positively charged nucleus with a negatively
  charged electron orbiting the nucleus
• 2) electron has angular momentum
• 3) electron can only change energy by
  absorbing/emitting electromagnetic radiation in
  integer units of nh/2?
• 4) radiation emitted/absorbed
• Nobel Prize in Physics - 1922
• "for his services in the investigation of the
  structure of atoms and of the radiation emanating
  from them"

9
Diffraction of Light
10
Albert Einstein

• Discovered that electrons are ejected from
  surfaces (typically metal surfaces) when light of
  a certain wavelength is transmitted to the
  surface
• no electrons are emitted if the light is below
  the threshold frequency
• intensity of the light only increased the
  electron flux
• energy of the emitted electron was the same
• Light can be thought of as a particle
• photons are quantized
• tails of comets always point away from the sun
• Nobel Prize in Physics - 1921
• "for his services to Theoretical Physics, and
  especially for his discovery of the law of the
  photoelectric effect"

11
Prince Louis-Victor Pierre Raymond de Broglie

• Extended the wave/particle duality of light to
  particles
• only small particles need apply
• electrons
• Ten page PhD thesis (1924) that explained his
  Nobel prize-winning research (mine was 300 pages
  and didnt win a Nobel Prize)
• committee didnt understand it
• sent to Einstein
• he said it was good
• In 1927 the Davisson-Germer experiment proved
  this hypothesis
• Nobel Prize in Physics - 1929
• "for his discovery of the wave nature of
  electrons

12
Max Planck

• Energy is directly proportional to frequency
• E h?
• initially believed this was only applicable to
  energy absorbed/emitted and not to
  electromagnetic waves
• Not widely accepted until
• Einstein used it to describe the photoelectric
  effect
• and Bohr used it in the development of the modern
  atom
• Nobel Prize in Physics - 1918
• "in recognition of the services he rendered to
  the advancement of Physics by his discovery of
  energy quanta"
• A new scientific truth does not triumph by
  convincing its opponents and making them see the
  light, but rather because its opponents
  eventually die and a new generation grows up that
  is familiar with it.
• It is impossible to make a clear cut between
  science, religion, and art. The whole is never
  equal simply to the sum of its various parts.

13
Erwin Schrödinger

• Responsible for quantum mechanics
• indirectly responsible for tears and ulcers of
  many physical chemistry students
• Mathematical description of the atom
• Describes the location of the electron as a
  wavefunction, ?
• The meaningful information that arises from
  solving the Schrödinger equation for an atom is
  ?2, the probability function
• Nobel Prize in Physics - 1933
• "for the discovery of new productive forms of
  atomic theory"

14
Periodic Table
15
Otto Stern and Walther Gerlach

• The orbitals that electrons occupy must take up
  specific orientations relative to a magnetic
  field
• Determined that electrons have spin
• 1/2 (spin up, ?) and -1/2 (spin down, ?)
• Otto Stern won the Nobel Prize in Physics - 1943
• "for his contribution to the development of the
  molecular ray method and his discovery of the
  magnetic moment of the proton"

Stern
Gerlach
16
Spherical Polar Coordinates