Radioactive Decay Lab Report

All kinds of rocks contain very small amounts of radioactive elements, these are unstable and they break down into more stable atoms over time, which is called radioactive decay. Scientists can tell how old a rock is by using radiometric clocks, or by looking at its absolute age. Geologists measure the amount of certain radioactive elements; as time passes the radioactive elements change at regular rates, into non-radioactive elements. The older a rock is the larger the number of elements. The age of the rock is found by measuring when the element decays.
Radio isotopes which are used to calculate the age of rocks have very long half-lifes, one of the most commonly used isotopes for this is uranium 238.
Uranium 238: Half life = 4.5 billion years
Uranium-238 decays by alpha emission into thorium-234, which itself decays by beta emission to protactinium-234The various decay products is a a series starting at uranium-238. After several more alpha and beta decays, the series ends with the stable isotope lead-206.
Since scientists know the rate at which uranium 238 becomes lead 206, they can determine the age of a rock that contains uranium 238 from the ratio of uranium 238 to lead 206 in the rock. They can calculate the age more accurately by measuring all the products in the series.
The two uranium-lead dates obtained from U-235 and U-238 have different half-lives, so if the date obtained from the two decays are in agreement, this adds confidence to the date. They are not always the same, so some uncertainties arise in these processes.
Uranium 235: Half life = 700 million