1. Chapter 4.4 and 25

2.  Lawrence’s cyclotron: http://www.lbl.gov/Science- Articles/Archive/early-years.html http://www.lbl.gov/Science- Articles/Archive/early-years.html  FermiLab http://www.fnal.gov/http://www.fnal.gov/  CERN http://public.web.cern.ch/public/http://public.web.cern.ch/public/ A.k.a. “Large hadron collider” (LHC)  SuperCollider http://www.hep.net/ssc/http://www.hep.net/ssc/

3. CHEMICALNUCLEAR  Bonds are broken or formed.  Atoms are unchanged, but rearranged.  Involve valence electrons.  Associated with small energy changes.  Reaction rate influenced by temp, pressure, concentration, catalysts.  Nuclei emit particles and/or rays.  Atoms are converted into atoms of another element.  Involve protons, neutrons, and electrons.  Associated with large energy changes.  Reaction rate not normally affected by temp, pressure, catalysts.

4.  Radiation – the rays and particles emitted by the radioactive material  Radioactive atoms undergo significant changes in their identity Atoms of one element change to atoms of another element  Reason? Nuclei are unstable Gain stability by losing energy

5.  Radioisotopes – isotopes of the same atoms with unstable nuclei  Undergo radioactive decay to become more stable  Most common radiation types: Alpha Beta Gamma

6.  Which atomic nuclei are radioactive?  Neutrons – add attractive force within the nucleus  Stability – related to balance between electrostatic and strong nuclear forces  Neutron/proton ratio Low atomic numbers ~1:1 ratio High atomic numbers ~1.5:1 ratio  Figure 25.8 p. 811

7.  Too many neutrons to be stable (above band of stability): Beta decay Alpha decay Gamma decay  Too few neutrons to be stable (below band of stability): Positron emission Electron capture

8.  Types of Decay Notes on Board….

9.  Radioisotopes have differing decay rates  Half-life – time required for one-half of a radioisotope’s nuclei to decay into its products  Example: Strontium-90 half-life (t) = 29 years Today - 10.0 g strontium 29 years from now – 5.0 g strontium

11.  Equation: amount remaining = initial amount (1/2) n OR amount remaining = initial amount (1/2) t/T t = time elapsed T = duration of one half life *** must have same units of time  Table 25.5 p. 818 Radioisotopes all have different half-lives