# How do scientists use half life in radiometric dating

### How do scientists use half life in radiometric dating

If the rocks have an interbedded lava flow or volcanic ash bed, it's gold.The older our sample is, the more daughter isotope it will contain relative to the parent.

The driveway was poured in 1950, and the coins are all dated 1920. Radiometric dating generally requires that a system be closed - in other words, has not had material added or removed.

When t = 0, ln N(0) = C Taking exponentials of both sides, we get N(t) = N(0)exp(-Kt) If t = one half life, then N(t)/N(0) = 1/2 = exp(-Kt), and: ln(1/2) = -ln2 = -Kt, so t = ln2 / K So what we do in practice is determine the decay constant and calculate half life from it.

If the decay constant is very small, even tiny amounts of contamination by other radioactive materials can be very significant.

Potassium-argon dating is very susceptible to resetting because the argon decay products are merely held in place mechanically by surrounding atoms.

Argon, an inert gas, is not chemically bonded to neighboring atoms at all, and even minor thermal disturbance allows them to escape.

We could be sure that a mineral containing parentium originally had no daughterium.

If the mineral contained 1 part per million Parentium-123 and 3 parts per million Daughterium-123, we could be sure all the Daughterium-123 was originally Parentium-123.

If you don't have minerals with those elements, you can't date the rock.

In particular, quartzites and carbonate rocks almost always don't have enough to permit dating.

Imagine we have an undiscovered element, Parentium, that has a radioactive isotope, Parentium-123, which decays to stable Daughterium-123.

This is the only way Parentium-123 decays, and there is no other source of Daughterium-123.

Furthermore, Parentium and Daughterium are so different in chemical properties that they don't otherwise occur together.