 What are the limitations of relative age dating?  What do you think Absolute age dating is?

 Absolute age dating determines the actual age of rocks, fossils, or other objects.  Radioactive isotopes of igneous and metamorphic rocks (some fossils) have a known decay rate that scientists use to calculate the age of the rocks.  Why is sedimentary rock not used?

 Radioactive substances breakdown at a constant rate, changing the number of protons and neutrons.  When the number of protons and neutrons is changed, a new element is made.

 The original radioactive element is called the “parent”  The new element is the “daughter”  The change of radioactive elements (“parent”) into other elements (“daughter”) over time is called radioactive decay.

 When radioactive elements begin to emit atomic particles, it will do so at the same rate no matter the environment it is in. › temperature, pressure, and other physical changes have NO effect.  Radiometric dating is when scientists compare the amount of parent nuclei with daughter nuclei.

 Half-life is the time it takes for half of the parent nuclei to turn into daughter nuclei.  One half-life may take seconds, or billions of years.

 A common isotope to use is Carbon-14. › C-14 decays into stable Nitrogen-14.  Its half-life is 5730 years and is useful for rocks or bones YOUNGER than 700,000 yrs.  If C-14 has a half-life of 5730 yrs. And a rock sample contains 1/8 th of its original amount of C-14. How old is the sample?

 Alpha decay occurs when a radioactive isotope emits an alpha particle › Alpha particle = 2 protons and 2 neutrons  How are the mass number and atomic number affected?

 Beta decay involves electrons, and can have two forms: positive and negative.  Negative Beta decay is when a neutron becomes a proton within the nucleus. › mass is unchanged and the atomic number is +1.  Positive Beta decay is when a proton turns into a neutron within the nucleus. › mass is unchanged and the atomic number is -1.

 Uranium 238 is often used in Alpha and Beta decay › eventually turns into Lead 206 › takes 4.5 Billion years

 Gamma decay occurs because the nucleus is at too high an energy. The nucleus falls down to a lower energy state and, in the process, emits a high energy photon known as a gamma particle.