4. “I can’t be hurt by something I can’t see or feel.”
                                      Too much radiation can indeed be harmful. Just because
                                      it isn’t visible doesn’t mean it isn’t real.
                                5. “All uranium can be used as nuclear fuel.”
                                      Only the ²³⁵U isotope of uranium is fissionable; most uranium
                                      ore (>90%) is ²³⁸U, which is not fissionable.
                                6. “The number of counts from a Geiger counter is equal to the number
                                      of nuclei that decay.”
                                      The Geiger counter detects and records only a small fraction of particles
                                      emitted from decaying nuclei. Some reasons for this inability to count all
                                      disintegrations are:

                                             a.   Window thickness of the Geiger tube. Not all particles will penetrate the
                                                   tube.
                                             b.   Geiger tube dead time. While the tube is busy reacting to a particle, other
                                                   particles go undetected.
                                             c.   Counter geometry. Radioisotopes emit radiation in all directions (4-p
                                                   geometry). A typical Geiger tube can only monitor a small fraction or
                                                   small angle of all the radiation direction angles.

                                                 A typical counter only counts the relative number of disintegrations.

                  Pattern Recognition/Problem Solving

                                1.  To balance nuclear equations, conservation of both mass number and
                                     charge on the nucleus must be achieved. Mass number (A) is the sum of the
                                     numbers of protons and neutrons in the nucleus. It is also the approximate
                                     mass of a particle or isotope to the nearest whole atomic mass unit, u.
                                     Charge is the positive or negative whole units of electrical charge. One unit
                                     equals 1.60 x 10 ^–19 C (coulombs).

                                2.  Nuclear Symbols. — ^A_Z X
                                     A = mass number, and Z = positive charge on nucleus or
                                     A = sum of the protons and neutrons, and Z = number of protons
                                     e.g., for ²³⁸₉₂U   238 = mass number, and 92 = charge on nucleus or
                                                               238 = protons + neutrons, and 92 = protons

                                other:
                                      proton: ¹₁H                          electron: ⁰_–1e                            neutron: ¹₀n

                                      alpha (a) particle: ⁴₂He         beta (b or b – ) particle: ⁰_–1e     positron (b + ): ⁰₊₁e

                                3.  Balancing Nuclear Equations. — In a nuclear equation charge and mass
                                     must be conserved.

                                     Examples:

                                     a. Alpha radiation ( ⁴₂He emitted from nucleus)
                                                                                            ²³⁸₉₂U => ⁴₂He + ^A_ZX
                                         238= (4 + A)                      A must be 234 (conservation of mass number)
                                          92 = (2 + Z)                       Z must be 90 (conservation of charge)
 
 
 
 

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