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Science Dept.

Chemistry CHE 100 Notes
D. The Structure of the Atom

1. Atomic Mass (or Atomic Weight)
   1. Units of Atomic Mass are based on the Carbon 12 atom

   2. 1 amu or Atomic Mass Unit = 1/12 C¹²

2. Dalton's Atomic Theory (1767 - 1844)
   1. *

   2. *

   3. *

   4. *

   5. *

3. Sub-atomic Particles
   1. The Neutron, n^o

   2. The Proton, p⁺

   3. The Electron, e^-

4. Nuclear Arrangement
   1. The Nucleus contains:
      1. Most of the mass of an atom resides in the nucleus.

      2. The nucleus has a positive charge.

   2. The Nucleus contains:
      1. Protons

      2. Neutrons

   3. The atom is electrically neutral. The # p⁺ = # e^-

   4. The Electrons are found outside of the nucleus in certain energy levels or certain "orbits".

5. Atomic Number
   1. The Atomic Number defines the element.

   2. The Atomic Number is equal to the number of protons in the nucleus.

6. Atomic Mass or Weight
   1. The Atomic Mass defines the isotope (weight variety) of an element.

   2. The Atomic Mass is equal to the number of protons and the number of neutrons in the nucleus.

7. Symbols
   1. ^A_ZE

   2. E is the symbol for the element (eg. He is Helium)

   3. A = Mass Number (number protons + neutrons)

   4. Z = Atomic Number (number of protons)

   5. Give the symbol for common Hydrogen:

       
      

   6. Give the symbol for common Helium:

       
      

   7. Give the symbol for common Boron:

       
      

8. Isotopes

   1. The Isotopes of Hydrogen:

      1. Hydrogen

          
         

      2. Deuterium

          
         

      3. Tritium

          
         

9. Radioactivity
   1. Definition:

   2. Half-Life:

   3. Natural Radioactivity vs Induced Radioactivity

   4. A Natural Radioactive Series - Three Great Clocks:
      1. U²³⁸ to Pb²⁰⁶

      2. U²³⁵ to Pb²⁰⁷

      3. Th²³² to Pb²⁰⁸

   5. Carbon 14 Dating

   6. Three Rays:
      1. Alpha Rays:

      2. Beta Rays:

      3. Gamma Rays:

10. How About a Quick Quiz?