Which quantity helps determine the absolute age of rocks and fossils?
A. The ratio of carbon -12 to carbon -14
B. The difference between the amounts of carbon -12 and carbon -14.
C. The ratio of protons to neutrons in carbon -14.
D. The difference between the number of protons and neutrons in carbon -14.
C. The ratio of protons to neutrons in carbon-14.
The correct answer is B. The difference between the amounts of carbon -12 and carbon -14.
The correct answer is C. The ratio of protons to neutrons in carbon-14.
To determine the absolute age of rocks and fossils, scientists use a process called radiometric dating. Radiometric dating relies on the properties of certain isotopes, which are variants of an element with different numbers of neutrons.
Carbon-14 is one such isotope that is commonly used for dating organic materials. It has 6 protons and 8 neutrons, giving it a total atomic mass of 14. Over time, carbon-14 undergoes radioactive decay, meaning it gradually transforms into another element, nitrogen-14. This process occurs at a predictable rate known as the half-life of carbon-14, which is about 5730 years.
By measuring the ratio of carbon-14 to carbon-12 (a stable isotope of carbon) in a sample, scientists can estimate how long it has been since the organism died. As carbon-14 decays, the amount of carbon-14 decreases, while the amount of carbon-12 remains constant. By comparing the ratio of carbon-14 to carbon-12 in a sample with the known rate of decay, scientists can calculate the absolute age of the sample.
Therefore, the ratio of protons to neutrons in carbon-14 is a crucial factor in determining the absolute age of rocks and fossils through radiometric dating.