ATOMIC STRUCTURE AND THEORY

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ATOMIC STRUCTURE AND THEORYNUCLEAR CHEMISTRY

• CHAPTERS 4 25

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Early Models of the Atom

• Democritus (450 BC) Matter is composed of tiny
  indivisible particles.
• Daltons Atomic Theory (1803) Based on four
  statements.
• Each element is composed of atoms.
• Atoms of the same element are alike and differ
  from any other element.
• Atoms can not be created nor destroyed by
  chemical reactions.
• Atoms combine in simple whole number ratios.

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• Atom The smallest particle of an element that
  retains the chemical identity of that element.
• Approximately 114 elements. The alphabet of
  chemistry.
• The chemists goal is to understand the atoms
  that make up the world.

4
Discovering Atomic Structure

• Magnetism The theory for the discovery of the
  electron and proton.
• Electrostatics Opposite charges attract and
  likes repel.
• Benjamin Franklin An object could have one of
  two charges (positive or negative).
• Michael Faraday (1839) Drew the connection
  between the electrical current and the structure
  of the atom.

5
Equipment to Isolate Sub-Atomic Particles

• Eugene Goldstein Designed the cathode ray tube
  and the canal ray tube.
• Vacuum inside, current flows between cathode and
  the anode (blue), source of electrons or x-rays.

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Discovery of the ElectronJ.J. Thompson

• Defines the charge of the electron.
• Designs the mass spectrometer.
• Begins to define the mass of the electron.
• Places bar magnets around the tube and creates a
  magnetic field in which the beam of blue light
  bends toward the positive pole of the magnet.

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Defining the ElectronRobert Milikan

• Defines a more accurate mass of the electron.
• Oil Drop Experiment
• Timed the rate at which the charged oil drop
  would rise and fall depending upon the strength
  of the electromagnetic field vs. the strength of
  gravity.

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Discovery of the Proton

• Eugene Goldstein Defined the charge of the
  proton.
• J.J. Thompson Defined the mass of the proton to
  be 1837 times the mass of the electron.

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The Nuclear AtomRutherford

• Gold Foil Experiment
• Concluded a nucleus existed.
• Contained the positive charge as well as the
  majority of the mass.

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Atomic Structure

• Atoms are composed of protons, neutrons, and
  electrons.
• Create chart on the board of sub-atomic particles
  for comparison.

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Atomic Number and Mass

• Atomic number Z of protons.
• Atomic mass M of protons and neutrons.
• An individual atom is electrically neutral.
• Protons Electrons.
• p Z, Charge p - e, and n M Z.

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IONS

• Created when an atom gains or loses one or more
  electrons.
• It acquires a net electrical charge.
• Charge of ion the number of protons the
  number of electrons.

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Isotopes

• Daltons postulate that all atoms of a given
  element are identical is not exactly true.
• An isotope is an atom that has the same number of
  protons but a different number of neutrons.

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Periodic TableDevelopment

• Why?
• Mendeleev
• Based on increasing atomic mass.
• Predictions.
• Moseley
• Based on increasing atomic number.
• Why did Mendeleevs work?
• Periodic Law When elements are arranged in
  order of increasing atomic number, their physical
  and chemical properties show a periodic pattern.

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• Metals Properties include luster or shine, good
  conductors of heat/electricity, malleable, and
  ductile.
• Nonmetals Large variation in properties.
• Metalloids or Semimetals The in between.

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• Family Names
• Representative (1A 8A)
• Transition (1B 8B)
• Inner Transition
• Alkali Metals
• Alkaline Earth Metals
• Boron family
• Carbon family
• Nitrogen family
• Oxygen family
• Halogens
• Noble gases

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Nuclear ChemistryThe Changing Nucleus

• Strong Nuclear Force between extremely close
  subatomic particles.
• Atomic s 1 thru 20 protons neutrons.
• Past 20 Need more neutrons than protons to be
  stable.
• Past 83 All are radioactive.
• Too many or too few neutrons radioactivity.

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RadioactivityAlpha, Beta, and Gamma

• Distinguished by charge, mass, and penetrating
  power.
• Radioactive decay when an atom emits one of
  these kinds of radiation.
• Decay nucleus decays to form a new nucleus
  releasing radiation in the process.
• Nuclear reactions change the composition of the
  atoms nucleus.

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Types of Radiation
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Nuclear Equations

• Keep track of the reactions components.
• The sum of the mass numbers and atomic numbers
  are the same before and after.
• Sample problems.

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Effects of Radiation

• Harmful to living things
• Effects depend on the amount and type.
• Effects on living tissue
• Ionizing radiation disrupts living cells.
• Somatic damage direct.
• Genetic damage reproduction.

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Uses of Nuclear Chemistry

• Radioactive dating.
• Smoke detectors.
• Imaging.
• Radiotracers.
• Cancer therapy.
• Food preservation.
• Energy.

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Measuring Radiation

• Equipment
• Dosimeter.
• Geiger counter.

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Nuclear EnergyNuclear Fission

• A large nucleus is split into two smaller nuclei
  of approximately the same mass.
• The missing mass energy.
• Nuclear chain reactions.
• Nuclear reactors.
• Three Mile Island (loss of coolant).
• Chernobyl (failure of the moderator).
• Waste disposal (fuel rods and burial).

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Nuclear EnergyNuclear Fusion

• Two small nuclei join to form a large nucleus.
• Difficult to produce and control.
• Electron cloud repulsion.
• Nucleus repulsion.
• Benefits
• Uses hydrogen abundant.
• No radioactive waste.
• Problem
• High temps required.

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Half-life

• The half-life of a radioactive isotope is the
  time it takes for one half of a sample of that
  isotope to decay.
• Uranium-238 4.5 billion years (alpha decay).
• Carbon-14 5,730 years (beta decay).
• Sample problems.