Transcript Slide 1

Chemistry Chapter 3
Atoms:
The Building
Blocks of Matter
Clicker ?
How long have people been interested in
understanding matter and its structure?
A. Thousands of years
B. Hundreds of years
C. A few years
D. Never
 Who: Aristotle, Democritus
 When: More
than 2000 years ago
 Where: Greece
 What: Aristotle believed in 4 elements:
Earth, Air, Fire, and Water. Democritus
believed that matter was made of small
particles he named “atoms”.
 Why: Aristotle
and Democritus used
observation and inferrence to explain the
existence of everything.
 Who: European
Scientists
 When: 800 – 900 years ago
 Where: Europe
 What: Their work developed into what is
now modern chemistry.
 Why: Trying to change ordinary materials
into gold.
Particle Theory
John Dalton
1766-1844
 Father of the atom
 Performed color blindness test
 Atomic Theory is a theory of the nature of
matter
 Dalton model (Billiard Ball Model)
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Dalton proposed the theory that elements are
composed of indestructible atoms.
Dalton stated that all atoms of one element were
exactly alike, but that atoms of different
elements were different form each other.
He believed that an atom’s weight indicated the
element to which it belonged and devised one of
the first tables of atomic weights.
He also believed that chemistry should be based
on the atom and advanced the idea that atoms
cannot be created or destroyed.
 Who: John
Dalton
 When: 1808
 Where: England
 What: Described atoms as tiny particles that
could not be divided. Thought each
element was made of its own kind of atom.
 Why: Building on the ideas of Democritus in
ancient Greece.
David Brooks
Ricky Getch
 He
performed
experiments with the
phosphorescence in
light bulbs and the
connection between
x-rays and naturally
occurring
phosphorescence.
 Spontaneous
radioactivity gasses
could ionize and be
deflected by electric
or magnetic fields.
 Won
the 1903 Nobel
prize in the field of
physics.
 Who: Henri
Becquerel
 When: 1896
 Where: France
 What: Discovered
radioactivity, the
spontaneous emission of radiation by a
material
 Why: Interested in fluorescence and
phosphorescence
Discovery of Electrons
J.J. Thomson
By: Averie and Chelsea
Discovery
• He discovered the electron and isotopes and he
was also credited for the discovery of the mass
spectrometer.
• Thomson’s experiments began in 1895, and
were influenced by James Clerk Maxwell
• Assumed that cathode rays exhibited a single
charge-to-mass ratio and must be made of a
single type of negatively charged particle, which
he called "corpuscles."
• Thomson is described as, “the man who first
split the atom.”
• J.J. Thomson was awarded the Nobel Peace
Prize in physics in 1906.
The primary function of
this experiment was to
see if the cathode ray
was positive or negative
because there was an
electrometer, a device
that measures the
charge of an object.
This was used to test the
conductivity of gas in the tube.
It would show if the particles
could separate.
The magnetic field was
produced with a Helmholtz
galvanometer. Because of
the magnetic fields, the
cathode ray is spread out.
If the electrostatic field is
increased, then the
magnetic field decreases
 Who: J. J. Thompson
 When: 1897
 Where: England
 What: Thompson
discovered that electrons
were smaller particles of an atom and were
negatively charged.
 Why: Thompson knew atoms were neutrally
charged, but couldn’t find the negative
particle.
Bree Porto
Ieshia Ross
Marissa Elam
Experiment
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“The way this experiment works
is that a droplet of oil will come
out of an atomizer and go through
a tiny slit in an electrode. From
the electrode the droplet will
pass into a chamber with an
electrode parallel from the
electrode it had just passed. In
this chamber Millikan was able to
balance or suspend the droplet
by the charge the droplet had
picked up when passing through
the air. Usining the amount of
voltage needed to suspend the
droplet he could then calculate
the charge the the droplet.”
-1896
http://library.thinkquest.org/28582/history/millexp.ht
m
Conclusion to Oil Drop Experiment
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When Millikan performed the oil drop
experiment when he sprayed a very
fine mist of oil and manipulated the
falling rate of the oil using x-rays. He
was able to measure the electron's
charge,
Millikan calculated the charge of an
electron to be -1.602x10-19 columbs.
Therefore, the mass had to be
9.109x1031 kg.
Since the electron was found to have a
negative charge, the implication
existed that there must be a positive
charge located somewhere in the
atom since atoms are naturally
neutrally charged.
 Who: R.A. Milikan
 When: 1909
 Where: USA
 What: In
his oil drop experiment,
determined the charge and the mass of an
electron.
 Why:Wanted to find the negatively charged
particles in an atom
 Discovered
the concept of the “nucleus”.
 Main studies were alpha particles.
 He was the first to deliberately turn one
element into another.
 He designed an experiment directing the alpha
particles towards a thin metal foil. Surrounding
the foil was a detector coated with a substance
that produced flashes when hit by a particle. It
was called “The Gold Leaf Experiment”.
 Who: Ernest
Rutherford
 When: 1911
 Where: England
 What: Conducted
an experiment to isolate
the positive particles in an atom. Decided
that the atoms were mostly empty space,
but had a dense central core.
 Why: He knew that atoms had positive and
negative particles, but could not decide
how they were arranged.
Ernest Rutherford
Atomic Structure II
Niel Bohr
Theory/Discoveries
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1915 Planetary Model
The Manhattan Project
Tube Alloy
Pictures
Planetary Model
Atomic Bomb
Nobel Prize
 Who: Niels
Bohr
 When: 1913
 Where: England
 What: Proposed that electrons traveled in
fixed paths around the nucleus. Scientists
still use the Bohr model to show the number
of electrons in each orbit around the
nucleus.
 Why: Bohr was trying to show why the
negative electrons were not sucked into the
nucleus of the atom.
Wave Nature of Atoms
Schrodinger
Jackie Raye, Kayla Byrom, and Emily
Boatwright
Schrodinger Wave Equation
Quantum Numbers:
 (1) Principle quantum
number, n, which gives
rise to energy levels.
 (2) Magnetic quantum
number, m, which gives
rise to sublevels.
 (3) Azimuthal quantum
number, l, which gives
rise to orbitals.
 (4) Spin quantum
number, s, which gives
rise to orbital pairs of
electrons.
 The equation accurately
predicts the behavior of
every electron in every
atom.
Theory: there is no single outcome
unless it is observed.
The outcome due to what the quantum
theory tells us that is true on a
microscopic level
vs.
The outcome due to what our observations
tell us on a macroscopic level.
Schrodinger’s Cat:
 Experiment:
Schrodinger’s Cat
Erwin Schrödinger
Taylor, ZAIN, Stephen
Schrödinger Accomplishments
 Nobel Prize: 1933 for work in Quantum Mechanics
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Schrödinger’s equation
 Worked with Einstein to develop: Schrödinger’s cat thought
experiment
Schrödinger Experiment
 Describes how the quantum state of a physical system
changes in time.
 The Schrödinger equation describes time in a way that is
inconvenient for relativistic theories.
Schrödinger Cat Thought
Experiment
 A thought experiment, often described as a paradox.
 The thought experiment presents a cat that might be alive
or dead, depending on an earlier random event.
 Who: Erwin
Schrödinger
 When: 1930
 Where: Austria
 What: Viewed
electrons as continuous
clouds and introduced "wave mechanics" as
a mathematical model of the atom.
 Why: He was dissatisfied with the quantum
condition in Bohr's orbit theory and he
believed that atomic spectra should really
be determined by some kind of equation.
Sir James Chadwick
October 1891- July 1974
Experiments
• Repeated experiments of the scientists
Fredric and Irene Joliot-Curie
• Looked for a neutral particle instead of
particle radiation
• Experiments were successful
• Called particle Neutron
Theory/ Discovery
• Discovered the Neutron by basing
experiments towards those of Fredric and
Irene Joliot-Curie
 Who: James
Chadwick
 When: 1932
 Where: England
 What: Discovered
the neutrally charged
part of the atom – the neutron.
 Why: Wanted to determine why atoms were
heavier than the protons and electrons
combined.
 Electrons
travel around the nucleus in
random orbits.
 Scientists cannot predict where they will be
at any given moment.
 Electrons travel so fast, they appear to form
a “cloud” around the nucleus.
Electron Cloud Model