Docstoc

Nuclear Chemistry 25.1 25.2

Document Sample
Nuclear Chemistry 25.1 25.2 Powered By Docstoc
					Nuclear Chemistry
25.1 Radiation
25.2 Nuclear Transformations


• Difference between radioactivity, radiation,
  radioisotopes
• Learn the three main types of radiation
• What is the band of stability?
• Radioactivity and half-life
                    Radioactivity
Discovered by Antoine Henri Becquerel in 1896
    – He saw that photographic plates developed bright spots
               when exposed to uranium metals
     The Experiment That Started it All




                                    They were studying effect of uranium salts
                                    that were exposed to sunlight and fogged
                                    photographic film. On cloudy day, he left
                                    uranium on film and it made this image.


Marie Curie and Antoine Becquerel-1896
         Definitions
• Radioactivity - Process by which
  substances give off the rays that
  fogged the photographic film
• Radiation - What the actual rays
  are called
• Radioisotopes - Unstable
  isotopes that become stable by
  emitting energy and radiation
                    The Radium Girls



Grace Fryer and the other women at the radium
factory in Orange, New Jersey, naturally supposed
that they were not being poisoned. It was a little
strange, Fryer said, that when she blew her nose, her
handkerchief glowed in the dark. But everyone knew
the stuff was harmless. The women even painted their
nails and their teeth to surprise their boyfriends when
the lights went out. They all had a good laugh, then
got back to work, painting a glow-in-the-dark radium
compound on the dials of watches, clocks, altimeters
and other instruments.
Three Main Types of Radiation


    • Alpha
    • Beta
    • Gamma
            Alpha Radiation

Loss of an -particle (a helium nucleus)

                  4
                  2   He
      238           234       4
       92   U   
                     90    Th+ He
                              2
Alpha Radiation
Beta Radiation
Beta Radiation
    Gamma Radiation
Loss of a -ray (high-energy
radiation that almost always
 accompanies the loss of a
       nuclear particle)

           0
           0
               
Radiation Comparisons
Band of Stability

           • Nuclei above this
             belt have too
             many neutrons.
           • They tend to
             decay by
             emitting beta
             particles.
       Stability of Nuclei
•There are no stable nuclei with an
  atomic number greater than 83.
  •These nuclei tend to decay by
          alpha emission.
                 Half-Life
  Half Life (t1/2) is the time required for half the
  atoms of a radioactive nuclide to decay.
Carbon-14 has a half life of 5715 years. If you
had 20 mg of C-14 the following would be true …

                              Amount C-14 left
         Years
                                  (mg)
         5715                       10
        11430                        5
        17145                       2.5
        22860                      1.25
        28575                     0.625

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:1
posted:5/6/2014
language:English
pages:17