Lab 4 Absolute Dating Techniques.docx - Radioactive decay is when atoms change into atoms of another element at known rates Some elements on earth’s

Lab 4 Absolute Dating Techniques.docx - Radioactive decay...

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Radioactive decay is when atoms change into atoms of another element at known rates. Some elements on earth’s crust are unstable. The nucleus of that unstable atom will spontaneously decay. When it does, a new atom will form. The original unstable atom is the parent and the more stable form that the parent decays into is the daughter. The half-life is the known rate at which half of the parent elements will decay. Below is a chart with radioactive parent atoms and their stable daughters. Radioactive Parent Stable Daughter Half Life Potassium 40 Argon 40 1.3 billion years Rubidium 87 Strontium 87 48.8 billion years Thorium 232 Lead 208 14 billion years Uranium 234 Thorium 230 245,500 years Uranium 235 Lead 207 704 million years Uranium 238 Lead 206 4.6 billion years Carbon 14 Nitrogen 14 5730 years To give you an example, when one half life of Uranium 234 has passed you will have half of the Uranium isotopes left and the other half will have decayed into Thorium 230. Say you have 100 Uranium atoms to start. After one half life, you would have 50
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Unformatted text preview: Uranium and 50 Thorium atoms remaining. But what happens when another half-life passes? Half of the 50 Uranium atoms would decay leaving you only 25. The 25 Uranium isotopes that did decay would increase your Thorium atoms to 75. Thus, after two half-lives, you have 25 Uranium and 75 Thorium atoms. After three half-lives, even more of the original unstable Uranium parent would decay leaving you with 12.5 in your sample and your Thorium atoms would increase to 87.5. Now let’s put some dates into this example. After one half-life, the age of your sample would be 245,500 years. After two half-lives, it would be 491,000 years old (245,500 x 2). After three it would be 736,500 years old (245,500 x 3). Now it's time for you to determine the ages, half lives, parent and daughter isotopes. Use the content in Chapter 6 to help you understand the concepts in this lab....
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