Chapter 17: Problem 29

What happens to the carbon-14 in a living organism when it dies? How can this be used to establish how long ago the organism died?

Short Answer

Expert verified

When an organism dies, its Carbon-14 isotope decays into nitrogen-14 at a rate determined by its half-life (5730 years). By measuring the remaining Carbon-14 and comparing to living levels, scientists can estimate the time of the organism's death.

Step by step solution

Understanding Carbon-14

Carbon-14, a radioactive isotope of carbon, is present in the atmosphere and taken up by living organisms during respiration. While an organism is alive, it maintains a constant ratio of Carbon-14 to Carbon-12 because it continuously exchanges carbon with the atmosphere. However, when an organism dies, it stops taking in carbon.

Decay of Carbon-14

After death, the Carbon-14 in the organism's remains slowly decays into nitrogen-14 through a process called beta decay. This radioactive decay follows a predictable pattern described by a half-life, which for Carbon-14 is approximately 5730 years.

Calculating the Time of Death

Scientists measure the amount of Carbon-14 remaining in the remains and compare it to the expected level in a living organism. Using the known half-life of Carbon-14, scientists can calculate the time elapsed since the death of the organism. This method is known as radiocarbon dating.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Carbon-14 Decay

Carbon-14 decay is essential to the field of archaeology and paleontology, providing a window into the past. This radioactive isotope of carbon is present in small quantities in the atmosphere and is absorbed by living organisms as long as they are alive.

Once an organism dies, the Carbon-14 atoms within it no longer replenish, because the exchange of carbon with the atmosphere halts. From this point, the radioactive Carbon-14 begins to break down at a predictable rate, which is where the notion of half-life becomes pivotal. The decay of Carbon-14 follows first-order kinetics, meaning the rate of decay is proportional to the amount of Carbon-14 remaining at any given time.

Radioactive Isotopes

Radioactive isotopes, or radioisotopes, are variants of chemical elements that have unstable nuclei and release energy in the form of radiation to achieve stability. Carbon-14 is one such radioisotope, which is naturally occurring and used extensively in radiocarbon dating.

Radioisotopes can decay through various processes, with beta decay being one of them. The importance of understanding radioactive isotopes lies in their diverse applications, ranging from medical treatments to determining the age of archaeological samples.

Half-Life

The half-life of a radioactive isotope is the time it takes for half of the isotope in a sample to decay. For Carbon-14, this period is approximately 5730 years.

The concept of half-life is crucial because it allows scientists to calculate the age of objects by measuring the remaining amount of the isotope and comparing it with the initial quantity — typically the ratio found in the atmosphere for Carbon-14. Knowing the half-life facilitates a reliable dating mechanism because the rate of decay is constant and independent of the initial size of the sample or the remaining amount after decay has begun.

Beta Decay

Beta decay is a type of radioactive decay where a beta particle, which is a high-speed electron or positron, is emitted from an atomic nucleus. In Carbon-14's case, this decay results in the transformation of a neutron into a proton, with the release of an electron and an antineutrino.

This process turns Carbon-14 into Nitrogen-14, another more stable element. Understanding beta decay enriches our comprehension of radioactive decay processes and is fundamental in the application of radiocarbon dating, as it sets the stage for measuring the decay of Carbon-14 in formerly living materials to estimate their date of demise.

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What happens to the carbon-14 in a living organism when it dies? How can this be used to establish how long ago the organism died?

Short Answer

Step by step solution

Understanding Carbon-14

Decay of Carbon-14

Calculating the Time of Death

Key Concepts

Carbon-14 Decay

Radioactive Isotopes

Half-Life

Beta Decay

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