# What does radioactive dating measurements

Radiometric dating is a means of determining the "age" of a mineral specimen by determining the relative amounts present of certain radioactive elements. By "age" we mean the elapsed time from when the mineral specimen was formed. Radioactive elements "decay" that is, change into other elements by "half lives.

The formula for the fraction remaining is one-half raised to the power given by the number of years divided by the half-life in other words raised to a power equal to the number of half-lives.

If we knew the fraction of a radioactive element still remaining in a mineral, it would be a simple matter to calculate its age by the formula. To determine the fraction still remaining, we must know both the amount now present and also the amount present when the mineral was formed.

Contrary to creationist claims, it is possible to make that determination, as the following will explain:. By way of background, all atoms of a given element have the same number of protons in the nucleus; however, the number of neutrons in the nucleus can vary.

An atom with the same number of protons in the nucleus but a different number of neutrons is called an isotope. For example, uranium is an isotope of uranium, because it has 3 more neutrons in the nucleus. It has the same number of protons, otherwise it wouldn't be uranium. The number of protons in the nucleus of an atom is called its atomic number. The sum of protons plus neutrons is the mass number.

We designate a specific group of atoms by using the term "nuclide. The element potassium symbol K has three nuclides, K39, K40, and K Only K40 is radioactive; the "What does radioactive dating measurements" two are stable. K40 can decay in two different ways: The ratio of What does radioactive dating measurements formed to argon formed is fixed and known.

Therefore the amount of argon formed provides a direct measurement of the amount of potassium present in the specimen when it was originally formed.

Because argon is an inert gasit is not possible that it might have What does radioactive dating measurements

in the mineral when it was first formed from molten magma. Any argon present in a mineral containing potassium must have been formed as the result of radioactive decay.

F, the fraction of K40 remaining, is equal to the amount of potassium in the sample, divided by the sum of potassium in the sample plus the calculated amount of potassium required to produce the amount of argon found. The age can then be calculated from equation 1. In spite of the fact that it is a gas, the argon is trapped in the mineral and can't escape. Creationists claim that argon escape renders age determinations invalid. However, any escaping argon gas would lead to a determined age younger, not older, than actual.

The creationist "argon escape" theory does not support their young earth model. The argon age determination of the mineral can be confirmed by measuring the loss of potassium.