Choose the explanation that does the following: (1) identifies the element used in carbon dating and (2) explains why the element is used.
A. iodine-131; iodine is present in the thyroid glands, is radioactive, and has a very long half-life
B. nitrogen-14; radioactive carbon turns into this after beta decay
C. carbon-14; it is present in every living organism, is radioactive, and has a very long half-life
C. carbon-12; it is the most abundant element in every living organism
Since it is called "carbon dating," you can automatically eliminate A and B. Whenever you don't know the right answer in multiple choice, you can get closer to the right answer by eliminating those that you know are wrong. The first C, carbon 14.
The correct choice for both (1) and (2) is C. Carbon-14 is the element used in carbon dating. It is present in every living organism, is radioactive, and has a very long half-life.
To explain further, carbon dating is a method used to determine the age of once-living materials. It relies on the fact that carbon-14 is a naturally occurring radioactive isotope of carbon. Carbon-14 is created in the atmosphere through interactions between cosmic rays and nitrogen-14. Once carbon-14 is formed, it combines with oxygen to become carbon dioxide and gets incorporated into the carbon cycle.
Living organisms constantly exchange carbon with the environment through processes like respiration and photosynthesis. As long as an organism is alive, it maintains a equilibrium between the amount of carbon-14 it takes in and the amount it loses. However, when an organism dies, it no longer takes in carbon-14 and the level of this isotope begins to decrease over time due to radioactive decay.
The half-life of carbon-14 is about 5,730 years, which means that after this time period, half of the original amount of carbon-14 will have decayed. By measuring the ratio of carbon-14 to carbon-12 (a stable isotope of carbon) in a sample, scientists can estimate the age of the sample. The decay of carbon-14 can be accurately measured using sensitive instruments, allowing for the determination of the age of samples that are up to about 50,000 years old.