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9th Grade Chapter 5 Lesson 2
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9th Grade Chapter 5 Lesson 2


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For Student Use Only

For Student Use Only

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  • 1. 9 th Grade Chapter 5 Lesson 2 Pgs. 120-131 For Student Use Only
  • 2. Inside the Atom
    • Atoms are made up of small particles called sub-atomic particles
      • Subatomic Particles
        • Found in Nucleus:
          • Neutrons- carry no charge
          • Protons- carry a positive charge
        • Atomic Number= number of protons in an element
        • Isotope= atoms with different numbers of neutrons
  • 3. Inside the Atom
    • Subatomic Particles:
      • Quarks- make up protons and neutrons
        • These were not known for a long time
        • There are 2 types of quarks:
          • Up quarks- has a 2/3 positive charge
          • Down quarks- has a 1/3 negative charge
          • It takes 3 quarks to make up a neutron or proton
  • 4. Inside the Atom
    • There is another component of the atom
      • Electrons- negatively charges particles
        • Electrons do not seem to make up anything else
      • Electrons are arranged in an electron shell.
      • Energy levels divide the electron shells
  • 5. Inside the Atom
    • Electron Shells
      • Electrons- energy levels hold more electrons and energy as they go farther away
      • When atoms have a charge:
        • Ions: an atom that lost or gained electrons
        • Anions: negative ions
        • Cations: positive ions
  • 6. Inside the Atom
    • Atoms-
      • Neutrinos- little neutral one
        • No electric charge and little mass
    • Atomic Models:
      • Illustrate the internal structure of the atom
      • The atoms originally were drawn like hard spheres
  • 7. Inside the Atom
    • Quantum Theory:
      • States that tiny particles such as electrons do not absorb or release energy in a smooth energy flow
      • Quantum: Energy is always absorbed or released in a discrete packet called a quantum
      • Electrons change shells or orbits as they gain or lose electrons.
  • 8. Inside the Atom
    • Bohr Model:
      • Most famous model of an atom
    • Wave-Mechanical Model:
      • Electrons have the same structure of both waves and particles
    • Heisenberg Uncertainty Principle:
      • Explains where a certain electron will be at a certain place
  • 9. Inside the Atom
    • Electron Cloud Model (aka- quantum mechanical model)-
      • Electrons do not have particular orbits, they are in a regions called orbitals
    • Atomic Measurement
      • Mass of Atom- this is the amount of “stuff” in an atom
      • Mass Number- number of protons and neutrons in an atom’s nucleus.
  • 10. Inside the Atom
    • Mass Number Notes:
      • Always whole numbers
      • Represent whole particles
      • More mass= higher mass number
      • Creates Isotopes- isotopes have same number of protons, but different number of neutrons and leads to different mass numbers
  • 11. Inside the Atom
    • Average Mass Number-
      • The isotopes (that exist naturally) are averaged together and relative to the percentage found in nature
      • It measures Atomic Mass Unit.
        • AMU= 1/12 the mass of a carbon-12 atom
  • 12. Inside the Atom
    • Atomic Mass:
      • The average of all the isotopes of an element
      • This is what chemists use when they say atomic mass
      • This is also called the mass number
  • 13. Inside the Atom
    • Nuclear Decay:
      • Isotopes of certain atoms give off radiation
      • Most atoms nuclei are stable, BUT some are not, the unstable atoms give off radiation
      • Unstable= an atom that is capable of changing into another atom
      • This unstable substance is called radioactive!
  • 14. Inside the Atom
    • Decay Rate:
      • Half-life= the rate at which an atom breaks down
      • There are 2 main types of Radioactive Decay + Gamma:
        • Alpha Decay- made up of 2 neutrons and 2 protons that are released from the center of the atom
        • Beta Decay- when a neutron changes into a proton and an electron is ejected from the atom
        • Gamma Radiation- not part of radioactive decay- usually occurs after alpha or beta radiation
  • 15. Inside the Atom
    • Radiation:
      • All types of radiation can affect human beings (in large amounts)
        • Alpha Particles:
          • Less dangerous- not as much energy
        • Beta particles:
          • More energy, more dangerous
        • Gamma Radiation:
          • Most powerful, most dangerous
  • 16. Inside the Atom
    • Radiation:
      • We are constantly opposed to radiation that occurs naturally
      • Our bodies naturally fix themselves
      • Above a certain amount of radiation cancer and other health problems may occur,
      • Below a certain level of radiation there is no harm done
  • 17. Inside the Atom
    • Radiation can be useful
      • How is radiation useful?
    • Nuclear Radiation:
      • Nuclear Fission:
        • In 1930’s discovered that by bombarding nucleus with neutrons they can split the nucleus
  • 18. Inside the Atom
    • Nuclear Fission:
      • The splitting of an nucleus releases large amounts of energy
        • Scientists discovered that by bombarding a nucleus with neutrons it will divide
      • Nuclear Fission- when a nucleus splits
      • Chain Reaction- The nucleus splits and the neutrons hit other nucleuses and causes them to split
  • 19. Inside the Atom
    • Nuclear Fission:
      • Critical Mass- there must be a certain amount of fissionable material to create a chain reaction
        • Uncontrolled Fission- in an atomic bomb
        • Controlled Fission- in a nuclear reactor it creates useful energy
        • Breeder Reactors- produce more nuclear fuel than they use
  • 20. Inside the Atom
    • Nuclear Fission:
      • Chernobyl- a site if a big accident caused by a series of mistakes
    • Nuclear Fusion:
      • The joining of nucleuses releases large amounts of energy
      • Sun is powered by fusion
      • Fusion is harder to produce than fission
      • Hydrogen Bomb is nuclear fusion