Radioactive Dating Radioactive Elements Absolute Time Involves elements
Radioactive Dating
Radioactive Elements & Absolute Time • Involves elements that give off radiation of unstable nuclei when they break apart
Chemistry Basics • Atoms make up everything • Molecules are two or more atoms combined chemically • Minerals are made up of molecules • Rocks are made up of minerals • Ions – atoms with either a positive or negative charge caused by the addition or removal of electrons • Isotopes – atoms of the same element with more neutrons
Radiation Types • 3 types Alpha Same structure as Helium 2 protons & neutrons Beta High speed electrons Gamma High frequency EM wave
Radioactive Decay • Primarily occurs with Alpha radiation • New lighter element formed with each alpha particle release • Decay continues until stable element reached • Called Daughter Product
• Time required for ½ of the atoms of a Half-Life radioactive element to decay to a stable end product
Uranium 238 Decay
Half-life Example Time = 0 After 1 half-life After 2 half-lives Parent Material =1 g Parent Material = 1/2 g Parent Material = 1/4 g After 3 half-lives Parent Material = 1/8 g After 4 half-lives Parent Material = 1/16 g
Half-Life Example
Radioactive dating • Allows geologists to determine the absolute age of non-living and living matter • There are two main types of radioactive dating – Radiocarbon dating – Radiometric dating
Radiocarbon • Uses isotope of carbon for dating Dating • Developed in 1947 • Only date organic material • Half-life C 14 = 5, 700 yrs
Radiocarbon • Good for dates back 100, 000 yrs before Dating present • Problems – Radioactive C 14 can’t be used on rocks – Half-life is too short – Half-life = 5700 yrs
Radiometric Dating • Uses radioactive isotopes to calculate the ages of rocks and minerals (non-living matter)
Radiometric Dating • U-238 – decays to Lead 206 – Half-life = 4. 5 billion years • Rubidium/Strontium – Half-life = 49 billion years – Can be used to date nearly all rocks • Potassium/Argon – Half-life = 1. 3 billion years
Solar System & Earth Dating • Age of our Solar System estimated by radiometric dating of meteorites • Earth age also comes from the dating of the Moon rocks ~4. 6 billion years old
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