1 / 15

Dating with Radioactivity

Dating with Radioactivity. Chapter 12, Section 3. Basic Atomic Structure. Each atom has a nucleus containing protons and neutrons and that nucleus is orbited by electrons Electrons have a negative electrical charge and protons have a positive charge Neutrons have no charge

daniellaw
Download Presentation

Dating with Radioactivity

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Dating with Radioactivity Chapter 12, Section 3

  2. Basic Atomic Structure • Each atom has a nucleus containing protons and neutrons and that nucleus is orbited by electrons • Electrons have a negative electrical charge and protons have a positive charge • Neutrons have no charge • The atomic number of an element is the number of protons in the nucleus, atoms of the same element always have the same atomic number • An atom’s mass number is the number of protons and neutrons in a nucleus • The number of neutrons can vary in a nucleus, and these variants, or isotopes, have different mass numbers

  3. Radioactivity • The forces that bind protons and neutrons together in a nucleus are usually strong • When nuclei are unstable, they spontaneously break apart, or decay, in a process called radioactivity • Radioactivity – the spontaneous decay of certain unstable atomic nuclei • An unstable radioactive isotope of an element is called the parent • The isotopes that result form the decay of the parent are called the daughter products • Radioactive decay continues until a stable or non-radioactive isotope is formed

  4. Common Types of Radioactive Decay

  5. Half-Life • Half-Life – the time for one half of the atoms of a radioactive substance to decay to its stable isotope • If the half-life of a radioactive isotope is known and the parent/daughter ratio can be measured, the age of the sample can be calculated

  6. Radioactive Decay Curve

  7. Concept Check • What is a half-life? • The amount of time necessary for one half of the nuclei in a sample to decay to its stable isotope.

  8. Radiometric Dating • Radiometric Dating – the procedure of calculating the absolute ages of rocks and minerals that contain radioactive isotopes • Each radioactive isotope has been decaying at a constant rate since the formation of the rocks in which it occurs • The products of decay have also been accumulating at a constant rate • As uranium decays, atoms of the daughter product are formed, and measurable amounts of lead eventually accumulate • An accurate radiometric date can be obtained only if the mineral remained in a closed system during the period since its formation • Although the basic principle of radiometric dating is simple, the actual procedure is quite complex

  9. Concept Check • Why is a closed system necessary in radiometric dating? • An accurate radiometric date can be obtained only if the mineral remained in a closed system since its formation.

  10. Dating with Carbon-14 • Radiocarbon (Carbon-14) Dating – method for determining age by comparing the amount of carbon-14 to the amount of carbon-12 • Carbon-14 is continuously produced in the upper atmosphere • It becomes incorporated with carbon dioxide, which is absorbed by living matter • All organisms—including you—contain a small amount of carbon-14; when an organism dies, the amount of carbon-14 gradually decays • By comparing the ratio of carbon-14 to carbon-12 in a sample, radiocarbon dates can be determined • Because the half-life of carbon-14 is only 5730 years, it can be used to date recent geologic events up to about 75,000 years ago • Carbon-14 is a valuable tool to anthropologists, archeologists, and historians

  11. Production and Decay of Carbon-14

  12. Concept Check • What is compared when dating with carbon-14? • The ration of carbon-14 to carbon-12.

  13. Importance of Radiometric Dating • Radiometric dating has produced dates for thousands of geologic events in Earth’s history • Rocks formed on Earth have been dated to be as much as 4 billion years old • Meteorites have been dated at 4.6 billion years old • Radiometric dating has supported the ideas of James Hutton, Charles Darwin, and many others who inferred the geologic time must be immense

  14. Assignment • Read Chapter 12, Section 3 (pg. 347-350) • Do Section 12.3 Assessment #1-6 (pg. 350)

More Related