1. Detection of Radioactivity and the Concept of Half-life  19.3

2. Geiger-Müller Counter  Detects high energy ions from radioactive decay  Uncharged Argon gas is found inside the Geiger counter Ions send electrical pulse Geiger counter counts how often the pulses are happening

3. Scintillation Counter  Instrument that detects radioactive decay  Every time decay events occur, the detector senses the flashes of light  Alternate way of detecting decay

4. Half-life  An important characteristic of a radioactive nuclide  Half-life: the time required for half the original sample of nuclei to decay  Lower half-life means more activity  Ex: a certain radioactive sample containing 1000 nuclei at a given time and 500 nuclei 7.5 days later, this radioactive nuclide has a half life of 7.5 days

5. Half-life  Example: 1 mole of Rubidium-223 becomes.5 mole of Rubidium-223 after 12 days 12 days would be the half life of Rubidium-223 The sample would be.25 mol of Rubidium-223 after 24 days

6. Dating by Radioactivity  19.4

7. Radiocarbon Dating  Radiocarbon dating: a technique for dating ancient articles made from wood or cloth Originated in 1940’s by Willard Libby  Radiocarbon dating is based on the radioactivity of C-14, which decays by - particle production Carbon-14 is continuously produced and decomposed through  particle production.  Creating a constant amount of C-14 in atmosphere

8. Radiocarbon Dating (cont.)  Used to date wood and cloth artifacts Every plant has Carbon-14, and there is a constant amount of Carbon-14 in the atmosphere  The amount of Carbon-14 that is present in the artifact is compared to the amount found in the atmosphere the half-life of Carbon is known to be 5730 years old