Which characteristic of potassium makes it useful for dating rocks?
It has a long half-life.
It decays at an unknown rate.
It produces lead as it breaks down.
It can be used to date all types of rock.
The characteristic of potassium that makes it useful for dating rocks is that it has a long half-life.
The characteristic of potassium that makes it useful for dating rocks is that it has a long half-life. Before diving into an explanation, let's first understand the basics of radioactive decay and half-life.
Radioactive decay is a process by which an unstable atomic nucleus loses energy by emitting radiation. This process occurs in certain isotopes, which are different versions of the same element that have different numbers of neutrons in their atomic nuclei. One such isotope of potassium is potassium-40 (K-40).
The half-life of a radioactive isotope is the time it takes for half of the atoms in a sample to decay. In the case of potassium-40, its half-life is approximately 1.3 billion years. This means that if you start with a certain amount of potassium-40, after 1.3 billion years, only half of that original amount will remain, with the other half having decayed into other elements.
Now, let's discuss how potassium's long half-life makes it useful for dating rocks. One common method of radiometric dating is called potassium-argon dating. It is particularly useful for dating rocks that are millions or billions of years old.
Potassium-40 decays into argon-40 through a process called beta decay. Argon-40 is a stable element and does not undergo further decay. By measuring the relative amounts of potassium-40 and argon-40 in a rock sample, scientists can determine how long it has been since the rock last solidified.
Since potassium-40 has a long half-life of 1.3 billion years, it can be used to date rocks of varying ages. This is one reason why potassium-argon dating is widely employed in geological and archaeological research.
To summarize, the characteristic of potassium that makes it useful for dating rocks is its long half-life. By measuring the relative amounts of potassium-40 and its decay product argon-40 in a rock sample, scientists can determine the rock's age.