The Relationship between Balancing Reactions and Reaction Lifetimes: A Consideration of the Potassium–Argon Radiometric Method for Dating Minerals

Knowing the mechanism for a chemical reaction means that you can also know what the products of that reaction are, how much of each product is formed, and the kinetics of product formation. Conversely, not knowing what the products are, how much of each product is formed, or the kinetics of product formation means that the mechanism of the reaction cannot be fully known. This line of thinking, commonly taught in college chemistry courses throughout the world, applies as well to nuclear decay reactions occuring in minerals. When a geochronologist determines a mineral's age by the potassium–argon method, it is implied that the mechanism(s) by which ⁴⁰Ar came to be inside the mineral are known. Yet, geochronologists never identify and quantify the other products that must form in addition to ⁴⁰Ar. In fact, no one even knows what the other products are, in any mineral. One may argue that, because most of the products from the potassium–argon reaction are unknown, the geochronologist cannot actually know how the ⁴⁰Ar atoms came to be inside the mineral and, hence, cannot fully know the mineral's age. Formulating and critically examining such arguments can be an important part of the education of scientists.