1. Announcements ● Exam 1—Chapters 1& 2 Wednesday. ● Download handout for next week's lab— Do prelab pages. To join clicker to class today: – Turn on the Clicker (the red LED comes on). – Push “Join” button followed by “20” followed by the “Send” button (switches to flashing green LED if successful). Some still need to sign up for e-mail discussion list— instructions in syllabus. ● Quiz 2, Monday (sections 1.6- 2.8).

2. Review Fusion in stars producing elements larger than H and He. – H fusion to get He in stars like our sun. – Multiple fusions in larger stars. Ends at 56 26 Fe Radioactive decay –above band of stability undergo  -decay –below undergo e - -capture or e + -emission, beyond undergo  -decay. Can get to Bi by n-capture and  -decay. Heavier than Bi, produced by rapid n-capture in supernovas. Common kinds of radioactive decay  and fission.

3. Radioactive Dating Expression for fraction left at time, t: Solving for t: t =t 1/2 {1/ln(0.5)}ln(A t /A o ) Carbon Dating –Use 14 C/ 12 C ratio for A t and A o –Use new sample to get A o Other isotopes: A o =stable product + remaining radionuclide; A t = remaining radionuclide.