Absolute Dating

Absolute dating provides a numerical age for the material tested, while relative dating can only provide a sequence of age. Absolute dating provides a numerical age for the material tested, while relative dating can only provide a sequence of age. It is a technique used to date materials, usually based on a comparison between the amount of original material and the amount of decayed material. It is a technique used to date materials, usually based on a comparison between the amount of original material and the amount of decayed material. So how does it work? So how does it work?

Remember that… All matter is made up of elements All matter is made up of elements All elements have an atomic number that indicates the number of protons in the nucleus All elements have an atomic number that indicates the number of protons in the nucleus Example… Example… Carbon has an atomic number of 6 (meaning it has 6 protons in its nucleus) Carbon has an atomic number of 6 (meaning it has 6 protons in its nucleus) Carbon also has 6 neutrons in its nucleus, so we call it Carbon 12 Carbon also has 6 neutrons in its nucleus, so we call it Carbon = 12, right ? 6+6 = 12, right ?

Chemistry Review Cont… Sometimes, an element can have an unequal number of protons and neutrons in it’s nucleus Sometimes, an element can have an unequal number of protons and neutrons in it’s nucleus The protons will stay the same, but the neutrons change The protons will stay the same, but the neutrons change If this is the case, we call it an isotope If this is the case, we call it an isotope Example… Example… Carbon 12 = 6 protons, 6 neutrons Carbon 12 = 6 protons, 6 neutrons Carbon 13 = 6 protons, 7 neutrons Carbon 13 = 6 protons, 7 neutrons Carbon 14 = 6 protons, 8 neutrons Carbon 14 = 6 protons, 8 neutrons

Radiometric Dating Some of these isotopes are unstable, and can lose parts protons, neutrons AND electrons (they decay). Some of these isotopes are unstable, and can lose parts protons, neutrons AND electrons (they decay). They do so at a constant rate, which can be recorded or observed. They do so at a constant rate, which can be recorded or observed.

Radiometric Dating Cont… If you change the number of protons or neutrons, the element changes. If you change the number of protons or neutrons, the element changes. We call the original element the “parent” element, while the new element is known as the “daughter” element. We call the original element the “parent” element, while the new element is known as the “daughter” element. Determining the ratio of “parent” material to “daughter” material is Radiometric/Absolute Dating! Determining the ratio of “parent” material to “daughter” material is Radiometric/Absolute Dating!

Half Life Because it can take a long time for the entire isotope to decay, scientists can study how long it takes “half” of the original amount to decay. Because it can take a long time for the entire isotope to decay, scientists can study how long it takes “half” of the original amount to decay. This is called its “Half-Life” This is called its “Half-Life”

Common unstable substances include… Carbon 14 > Nitrogen Carbon 14 > Nitrogen Uranium 238 > Lead 206 Uranium 238 > Lead 206 Potassium > Argon Potassium > Argon