Lead-207

Definition

Lead-207 is a stable isotope of the element lead, with 82 protons and 125 neutrons in its nucleus. It is the final product of the radioactive decay chain of uranium-235, making it an important isotope in the study of radiometric dating and the age of the Earth.

5 Must Know Facts For Your Next Test

1. Lead-207 is the stable end product of the uranium-235 decay series, which includes several intermediate radioactive isotopes.
2. The half-life of uranium-235 is approximately 704 million years, making it a useful tool for dating the age of the Earth and other geological formations.
3. The ratio of lead-207 to other lead isotopes, such as lead-206, can be used to determine the age of a sample through radiometric dating techniques.
4. Lead-207 is not radioactive and does not undergo further decay, making it a reliable indicator of the age of a sample.
5. The abundance of lead-207 in a sample, relative to other lead isotopes, can provide information about the geological history and formation of the Earth.

Review Questions

• Explain the role of lead-207 in the radioactive decay of uranium-235.
  • Lead-207 is the stable end product of the uranium-235 decay series. As uranium-235 undergoes radioactive decay, it transforms through a series of intermediate radioactive isotopes, ultimately producing lead-207. The accumulation of lead-207 in a sample can be used to determine the age of the sample through radiometric dating techniques, as the rate of uranium-235 decay is well-known.
• Describe how the ratio of lead-207 to other lead isotopes can be used to determine the age of a geological sample.
  • The ratio of lead-207 to other lead isotopes, such as lead-206, can be used to determine the age of a geological sample through radiometric dating. As uranium-235 decays, it produces lead-207 at a predictable rate. By measuring the relative abundance of lead-207 compared to other lead isotopes in a sample, scientists can calculate the time elapsed since the sample was formed, providing valuable information about the age and geological history of the Earth.
• Analyze the significance of lead-207 as a stable isotope in the context of radiometric dating and the age of the Earth.
  • The stability of lead-207 is crucial for its use in radiometric dating techniques. Unlike the radioactive isotopes that precede it in the uranium-235 decay chain, lead-207 does not undergo further decay. This makes it a reliable indicator of the age of a sample, as the amount of lead-207 present reflects the cumulative decay of uranium-235 over time. By studying the abundance of lead-207 relative to other lead isotopes, scientists can determine the age of geological formations and, ultimately, the age of the Earth itself, which is estimated to be around 4.54 billion years old.

Related terms

Radioactive Decay:

The process by which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves.

Uranium-235:

A naturally occurring isotope of uranium with 92 protons and 143 neutrons, which is the parent isotope in the decay chain that produces lead-207.

Radiometric Dating: A technique used to determine the age of rocks and minerals by measuring the decay of radioactive isotopes within them.