2. Democritus (465
BC)
• Ancient Greeks came to
believe all matter consisted of differing
amounts of only 4 basic substances: earth,
fire, water, and ether
• Leucippus, teacher of Democritus, proposed
matter was made of small particles
• D. was first to use the word atomos:
the smallest, indivisible part of matter
3. Back in the Iron Age….
• Some elements are found in nature in a
relatively pure form.
• Sulfur, copper, gold,
silver, and iron were
made into decorative
and useful objects.
4. The Alchemists (Dark Ages till
the Renaissance)
• Looked for the
philosophers stone
• thought they would
find a way to turn Pb
into Au
• Newton dabbled in
alchemy
5. The modern age begins
• Henning Brand of Germany discovered
phosphorus in 1669.
• He collected 50
buckets of urine,
fermented it, and
then boiled off the
water.
6. Joseph Priestley
• Discovers oxygen -1774
(at the same time as
Lavoisier & Scheel)
A “natural philosopher”
Also credited with
inventing soda water!
(1733-1804)
7. • Law of conservation of
Antoine Lavoisier mass
1743-1794 • Discovers nitrogen gas,
and that oxygen can be
chemically separated
from certain compounds
• confirms law of definite
proportions
• father of modern
chemistry
• loses his head to the
French Revolution
8. John Dalton
1766-1844
• Father of modern
Atomic Theory
• thought atoms of an
element were all
identical and
indivisible
• compounds are formed
from atoms of
different elements
10. William Prout
• Law of Definite
Proportions
1785-1850, a physician
Distilled HCl acid from
stomach juices, and
suggested that H is the
fundamental particle
11. Dimitri Mendeleev (1834-1907)
• Organizes the first
periodic table
• columns based on
valence (reactivity)
• position in a row
based (mostly ) on
atomic weight
• left places in table for
elements which were
not yet discovered
14. J J Thomson
1856-1940
• Discovers the electron
• Plum Pudding Model
of the atom….
• All the charged
particles were
randomly scattered
like “plums in
pudding”
• did not know about
neutrons
• Nobel Prize 1906.
Thompson's experiment to discover electrons (1897)
16. Wilhelm Roentgen
1845-1923
Discovered X-rays in 1895:
his wife’s hand
17. Becquerel
(1852-1908)
In 1896, Henri Becquerel discovered that
uranium salts emitted rays that resembled
X-rays in their penetrating power. He
demonstrated that this radiation, unlike
phosphorescence, did not depend on an
external source of energy, but seemed to
arise spontaneously from uranium itself.
Becquerel had, in fact, discovered
radioactivity.
18. The Curies
Pierre Marie
Marie (1867-1934) - first woman to win a Nobel Prize
Pierre (1859-1906) – died in traffic accident
Formulated the theory of radioactivity while working
with uranium; also discovered Polonium (named after
Poland) and radium
She was a pioneer in using radiation in medicine, but was
unaware of the hazards of radiation.
19. Nikola Tesla
1856-1943
•Investigated X-rays
•Got skin damage while
experimenting
20.
21. Ernest Rutherford (1871-1937)
• Electrons are separated
from the nucleus
• nucleus has positive
charge and the shells are
negative
• atoms are mostly empty
space (1911) - the
Gold foil experiment
• Planetary model
29. Erwin Schrödinger
1887-1961
• With Heisenberg,
calculated probable
locations of electrons
• Quantum mechanics
and Schrödinger ’s cat
30. Louis de Broglie
1892-1987
• Electrons orbiting the
nucleus exhibit wave
properties
• Moving matter has a
wavelength related to
its momentum
• Leads to development
of the cloud model of
the atom
33. Werner Heisenberg
1901-1976
• Mathematical models
with Schrodinger
• The Uncertainty
Principle
• you can not know both
the position and speed
of an electron
simultaneously
34. Heisenberg was a hydrogen filled nazi zeppelin that came to this
disastrous end in the 1930’s.
35. Werner Heisenberg was a German physicist who, in his late
twenties, introduced what is known as the Heisenberg
Uncertainty Principle. This discovery shook the very
foundation of subatomic physics.
36. Heisenberg’s principle states:
For any moment in time, it is
impossible to know the position and
the momentum of a moving particle.
Simply because the act of observing affects the behavior of the observed.
37. I’m sure you’re aware of some things that change their behavior
depending on how they are being observed, for example:
38.
39.
40. In the case of particles, the observer also affects the behavior of
the observed. There are limits to how much we can know about a
particle at any given moment. Take this picture for example:
Right now we can see the left side clearly.
However, if we moved the magnifying glass,
41. Now we can see the right side clearly but can no longer see the left.
42. Imagine this:
A microscope that can see electrons in orbit around the nucleus
We shoot ordinary light waves at the electron to find its
position, but the wavelength is too long to be obstructed by
the electron,so...
We try gamma rays (shorter wavelength).
The problem with this is that gamma rays have so much
energy (high frequency), that upon contact, the electron
is knocked out of orbit making impossible to know its
43. Albert Einstein
1879-1955
• A “slow student” who revolutionized
science and the world
• Mass is a form of energy!
E = mc2
44. Einstein didn’t like Quantum
Mechanics
• Einstein to Bohr, “God
does not play dice
with the universe”
• Bohr, in response,
“Who are you to be
telling God what to
do?”
45. Paul Dirac
Further developed quantum theory
from work of
Heisenberg and Schrodinger
Shared a Nobel Prize - 1933
Worked on Uranium
enrichment during WW II
46. James Chadwick
1891-1974
• 1932 discovers the
neutron
• Explains isotopes
http://www.nobel.se/physics/laureates/1935/chadwick-bio.html
47. Lise Meitner
1878-1968
• Realized that some
weight was lost during
nuclear fission: E=mc2
• Was part of the team
that discovered
nuclear fission in late
1930s
48. Enrico Fermi
(1901-1954)
• Emigrated from Fascist Italy in 1938 after
winning Nobel Prize
• Built first nuclear reactor – underneath the
stadium at the University of Chicago - 1942
49. Arthur Compton
1892-1962
Worked with Fermi on first reactor
Demonstrated the particle aspect of
electro-magnetic radiation:
The Compton Scattering Effect
50. Glenn T. Seaborg
1912-1999
• Responsible for the
Actinide concept
• Discovered ten elements:
plutonium, americium,
curium, berkelium,
californium, einsteinium,
fermium, mendelevium,
nobelium, and 106 (named
after him)
51. Radioactivity
Three types
• Alpha α – a He nucleus (2p+2n)
• Beta β – an electron
• Gamma γ – pure energy: EM waves
52. Penetration of Matter
• Though the most massive and most energetic of
radioactive emissions, the alpha particle is the
shortest in range because of its strong interaction
with matter. The electromagnetic gamma ray is
extremely penetrating, even penetrating
considerable thicknesses of concrete. The electron
of beta radioactivity strongly interacts with matter
and has a short range.
