Chapter 3 Atomic Theory

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Chapter 3Atomic Theory
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Early Theories

• 4 elements

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Democritus(460 - 370 BC)

• Greek philosopher
• Atomos indivisible particles
• Atoms are the smallest particle that retains the
  chemical identity

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The Greeks Used Logic

• The Greeks also believed in a combination of
  elements to make new things.
• For example Water and Earth Mud
• Mud might just seem like a nuisance to us, but
  back then it was a building material.
• Fire and Earth made Lava.
• If you are curious check out the Little Alchemy
  app (game) that can be found in Google Apps. It
  is a fun game.

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Jabir Ibn Haiyan (700? - 803 AD)

• Father of Chemistry
• Practiced Alchemy
• Discovered metals

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Antoine Lavoisier(1743 - 1794)

• Law of Conservation of Matter

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Joseph Louis Proust(1754-1826)

• Law of Constant Composition

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John Dalton (1766 - 1844)

• Atomic Theory
• This was the true start of our modern theory of
  matter.

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Daltons Theory

• Daltons ideas were a good start.
• However, we need to look at one of his postulates
  more closely.
• He stated that All atoms of the same atom are
  identical
• He didnt know about isotopes. The neutron
  wasnt discovered for another 130 years.

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Atomic Theory

• Elements made of atoms
• Atoms are identical of a given type of element
• Atoms neither created nor destroyed
• Compounds have fixed ratio of atoms

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Ben Franklin (1706-1790)

• Two types of charge positive () and negative (-)

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Michael Faraday(1791-1867)

• Atoms are related to electricity

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J.J. Thomson(1856 - 1940)

• Cathode Ray Tube (CRT) stream of electrons
• Plum Pudding Model

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cathode ray tube
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Thomsons Model

• This lead directly to the idea of electrons and
  was a major advancement in atomic theory.
• Sometimes this theory is called Raisins in a
  Plum Pudding.

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Robert Millikan(1838-1953)

• Determined charge mass of electron

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Henri Becquerel(1852 - 1908)

• Uranium exposes film

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Marie (1867-1934) Pierre Curie (1859-1906)

• Discovered radioactivity elements
• Radioactive decay

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Earnest Rutherford(1871 - 1937)

• Discovered radioactivity particles
• Discovered Nucleus
• Solar system model of atom

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Discovery of particles
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gold foil experiment
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Rutherfords Gold Foil Experiment

• There are animations on the website so that you
  can get a better visual of the experiment.
• Rutherfords experiment was truly a marvel.
• It answered a lot of questions and gave a good
  framework for future investigations.
• Remember that it was still a theory there is a
  long way to go in understanding an atom.

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Early Atomic Theory

• At this point, this completes our look at the
  early contributors into Atomic Theory and
  Structure.
• You were given a lot of names, but here are the
  ones I want you to focus on
• Democritus, Dalton, Thompson, Rutherford
• When we get to other topics, we will explore a
  few more of them in detail such as Becquerel and
  the Curies.

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Study Guide Help

• To assist you in your preparation, take note that
  I will not be asking much if anything about the
  following scientists
• Ben Franklin, Joseph Proust, Michael Faraday
• Robert Millikan, Jabir Ibn Haiyan, and Antoine
  Lavoisier might get a short question or two on a
  test or quiz.

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Niels Bohr (1885 1962)

• Electrons do not orbit like planets
• Described shells or energy levels
• Quantum theory

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H.G.J. Moseley (1887 - 1915)

• Discovered protons () in the nucleus
• Rearranged periodic table

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Sir James Chadwick (1891-1974)

• Discovered neutrons (0) in the nucleus

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Quarks, Quarks, Quarks (1950s present)

• 6 quarks have been discovered that make up
  protons and neutrons

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Protons

• Make up the nucleus
• Charge 1.602 x 10 -19C
• Mass 1.673 x 10 -24g
• Charge 1
• Mass 1 amu

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Neutrons

• Make up the nucleus
• Charge 0
• Mass 1.675 x 10 -24g
• Mass 1 amu

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Electrons

• Occur in electron Clouds
• Charge -1.602 x 10 -19C
• Mass 9.109 x 10 -28g
• Charge -1
• Mass 0 amu

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• Atoms are small but nuclei are smaller
• Diameter of a penny has 810 million copper atoms

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Atomic Number

• Number of protons in an atom
• Electrically neutral atoms have the same number
  of electrons as protons
• Ions are formed by gaining or losing electrons

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Isotopes

• Same number of Protons but different numbers of
  neutrons
• Mass number is the sum of the protons and the
  neutrons
• Isotopes have the same chemical properties
• Violates Daltons atomic theory

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Masses of Atoms

• 1 amu 1/12 mass of a 12C atom
• 99 Carbon 12C
• 1 Carbon 13C
• Average atomic mass of C is 12.01 amu
• Mass number is for one atom
• Listed as a decimal on the periodic table

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Nuclear Symbol
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Nuclear Reactions

• Nuclear reactions involve the nucleus of the atom
• Radioactivity is the spontaneous emission of
  radiation from an atom
• Nuclear reactions change elements involved

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Alpha Particle

• Alpha particle
• Helium nucleus with no electrons
• Will bounce off of paper and skin
• 2 charge

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Beta Particle

• Beta particle
• High energy electron
• Come from the decay of a neutrons
• Will penetrate skin
• Blocked by aluminum and Plexiglass
• -1 charge

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Gamma Radiation

• Gamma Rays
• High energy wave
• No charge
• No mass
• Penetrates skin, damages cells and mutates DNA
• Blocked by lead

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Nuclear Stability

• Most elements have a stable nucleus
• A strong nuclear force holds protons and neutrons
  together
• Neutrons act as the glue holding the protons
  together

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Nuclear Equations

• Scientists use a nuclear equation when describing
  radioactive decay
• The mass number and atomic number must add up to
  be the same on both sides of the equation

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Beta Decay

• Beta decay results in an increase in the atomic
  number

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Practice

• Write the nuclear equation of the alpha decay of
  Radon 226
• Write the nuclear equation of the alpha decay of
  Gold - 185

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Practice

• Write the nuclear equation of the beta decay of
  Iodine - 131
• Write the nuclear equation of the beta decay of
  Sodium - 24

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Chapter 24Applications of Nuclear Chemistry
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Half Life

• Radioisotopes are radioactive isotopes of
  elements (not all isotopes are radioactive)
• A half-life is the amount of time it takes for
  one half of a sample to decay.
• http//lectureonline.cl.msu.edu/mmp/applist/decay
  /decay.htm

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Beta Decay of Phosphorous - 32
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Radiocarbon Dating

• Carbon - 14 undergoes beta decay
• Half life of 5,730 years
• Used to approximate ages 100 30,000 years
• Other radioisotopes are used to measure longer
  periods of time

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Parent Daughter Half Change in...
Carbon-14 Nitrogen-14 5730 years
Uranium-235 Lead-207 704 million years
Uranium-238 Lead-206 4,470 million years
Potassium-40 Argon-40 1,280 million years
Thorium-232 Lead-208 14,010 million years
Rubidium-87 Strontium-87 48,800 million years
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Nuclear Bombardment

• Nuclear scientists make nuclei unstable by being
  bombarded with particles
• Also known as particle accelerators or atom
  smashers

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Radiation

• SI units are in Curies (Ci)
• One Curies is amount of nuclear disintegrations
  per second from one gram of radium
• Also measured in rem (Roentgen equivalent for man
• Over 1000 rem is fatal
• Detected by a Geiger counter

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Nuclear Power

• Nuclear Reactors use fission of Uranium-235 as
  source of energy
• A large nucleus is split into two smaller nuclei
• A small amount of mass is converted to a
  tremendous amount of energy
• 1 lb Uranium 235 1 million gallons of gasoline
• http//people.howstuffworks.com/nuclear-power2.htm
  

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Nuclear Fusion

• 2 atomic nuclei fuse releasing a tremendous
  amount of energy

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Nuclear Weapons

• Source of energy is Plutonium or Hydrogen
• Can be fusion or fission

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Gun-triggered fission bomb (Little Boy -
Hiroshima), Implosion-triggered fission bomb
(Fat Man - Nagasaki),







http//people.howstuffworks.com/nuclear-bomb5.htm