Nuclear Chemistry

1. Nuclear Chemistry

2. Electromagnetic Radiation Two types of radiation: 1.  Ionizing radiation      a.  x-rays, gamma rays     b.  greatest energy      c.  high frequency; short wavelength      d.  cause particles like electrons to be ejected      e.  exposure can cause great damage to tissues  2.  Non-ionizing radiation      a.  radio waves, microwaves, infrared, visible light, ultraviolet      b.  lower energy      c.  low frequency; long wavelength      d.  exposure does not cause great damage to tissues

3. Atoms ParticleSymbolLocationChargeMolar Mass (g/mol)protonp+nucleus1+1neutronnonucleus01electrone-outside nucleus in energy levels1-0.0005 or 0              A. atomic number = number of protons             B.  mass number = number of protons + neutrons             C. isotopes                         1.  atoms of the same element having different number of neutrons                         2.  radioisotope                                     a.  radioactive                                     b.  decays spontaneously 3.  symbol                   mass # à       90                                                                             Sr                                                 Atomic #  à    38 4.  name                         a.  add mass number to the name of the element                         b.  example:  strontium-90  or Sr-90

4. Radioactive Decay:Alpha Emission 1.  alpha particle is composed of 2 protons and 2 neutrons 2.  nucleus of helium-4 atom 3.  more massive than beta particle 4.  poor penetrating power 5.  slow speed 6.  potential to cause great damage to tissue 7.  produces new particle with lower atomic # and mass # 8.  symbols of alpha particle 42He     and    α 9. example of alpha decay 22688Ra   42He   +   22286Rn

5. Radioactive Decay:Beta Emission 1.  beta particle is an electron 2.  beta emission is equivalent to the conversion of a neutron to a proton 3.  smaller than an alpha particle 4.  moves faster and penetrates better than alpha 5.  produces new particle with higher atomic # and same mass # 6.  symbols of beta decay 0-1e      and      0-1β      and       β 7.  example of beta decay 146C   0-1e   +   147N

6. Radioactive Decay:Gamma 1.  gamma is a form of electromagnetic radiation 2.  high energy photons 3.  represents energy lost when the remaining nucleons reorganize into more stable arrangements 4.  moves at speed of light 5.  not a particle 6.  penetrates best of all types of radiation 7.  no change in particle that undergoes gamma decay 8.  symbols 00γ     and       γ

7. Radioactive Decay:Positron Emission 1.  positron is a positive electron 2.  produces a new particle with lower atomic # and same mass # 3.  positrons have a very short life because it is annihilated when it collides with an electron, producing gamma rays 01e   +   0-1e      2 00γ 4.  example of positron  emission 3819K   3818Ar   +   0+1e

8. Radioactive Decay: Electron Capture 1.  only type of radioactive decay in which the particle is on the reactant side of the equation (electron is consumed rather than formed) 2.  electron 3.  converts a proton to a neutron 11p   +   0-1e   10n 4.  example of electron capture 10647Ag   +   0-1e   10646Pd

9. Half-Life A.  Rate of decay of radioisotopes B.  Time required for half the atoms of a radioactive nuclide to decay C.  Pre-AP Radioactive Decay      1.  rate of decay = # of atoms that disintegrate per time      2.  A = KN           where A  =  activity  =  # disintegrations /time                      k  =  decay constant   (specific to isotope)                     N  =  number of atoms                      Nt  =   # radioactive atoms after time t                      N0  =  # radioactive atoms at time 0            Determined by                      ln Nt   =   -kt              ln = natural logarithm                           No            When t = half-life the t = t1/2     and   t1/2  =  0.693                                                                                       k