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Radioactive Decay of Dead Organisms

Radioactive Decay

Carbon-14 is a radioactive Isotope of Carbon-12. How many protons and neutrons are in the nucleus of C-12? __________ In C-14 ___________ While an organism is alive, the ratio of Carbon-14 to Carbon-12 is in equilibrium. This does not mean that there are equal amounts of C-14 and C-12, but rather, their proportion (ratio) to each other is constant. However, when the organism dies, no more C-12 is absorbed and the C-14 begins to decay. This decay changes the ratio. We know that C-14 is a beta emitter, so it will decay into ______________?

1. Draw a graph (in Excel) depicting C-14 decay as follows:
- Start with 100% C-14. 0%N.
- Show amounts (in percent) of C-14 for four (4) half lives.
- Show corresponding amounts of Nitrogen for each of those points.

2. If this organism were found to have died 11,400 years ago, what would be the ratio of Carbon: Nitrogen?

3. If this organism has a 3:1 ratio of N:C-14, how long ago might this organism have died?

4. Do you see a pattern here similar to any others in this activity? Explain.

5. Why do we keep referring to when the organism "died" rather than "how old" in analyzing C-14 decay?

Solution Preview

Radioactive Decay

Carbon-14 is a radioactive Isotope of Carbon-12. How many protons and neutrons are in the nucleus of C-12?
Carbon is atomic number 6, therefore there are 6 protons.

In C-14:
C-12 has 6 protons and 6 neutrons.
C-14 has 6 protons and 8 neutrons.
While an organism is alive, the ratio of Carbon-14 to Carbon-12 is in equilibrium. This does not mean that there are equal amounts of C-14 and C-12, but rather, their proportion (ratio) to each other is constant. However, when the organism dies, no more C-12 is absorbed and the C-14 begins to decay. This decay changes the ratio.

We know that C-14 is a beta emitter, so it will decay into N-14 and gives off a beta particle (a beta particle is just an electron).

FYI:
In other words one of the neutrons in C-14 decays into an electron and a proton. The result is N-14 which ...

Solution Summary

Solution is 650 words and includes Excel sheet with graph.

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