Lab 4 Radioactive (absolute) dating As it explained earlier. dating o.docx

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Lab 4 Radioactive (absolute) dating As it explained earlier.dating or ondering of rock units deposition or geologicalevents can be done either by relative dating or by radiometricor radioactive dating. RADIOMETRIC DATING is theprocess by which the absolute ne of a rock or geologic eventis determined. This is done using radioactive ISOTOPES,which are composed of ATOMS having the SAME NUMBEROF PROTONS but NOT having the SAME NEUTRONNUMBER, such as, Uranium (U), Potassium (K), Rubidium(Rb), and Thorium (Th), which are called PARENTISOTOPES, and desay by emitting nuclear particles. In thedecay process they are transformed into new isotopes ofdifferent elements called DAUGHTER PRODUCTS,Eventually, all radianctive isotopes decay to a stable daughterisotopes. For example, parent uranium isotopes decay througha series of steps to isotopes of lead and parent potassiumisotopes decay to calcium and argon. ATOMIC NUMBER: isthe number of protons in the nucleus of an atom written asthe subscript of the atom. If it is changed a new element isproduced ATOMIC MASS NUMBER: is the sum of thenumber of protons and neutrons in the nucleus of an atomwritten as the superscript of the atom. If it is changed no newelements are produced but a new isotope of the element isproduced. 238Atomic mass number 92 -_ Atomic numberRadioactive decay proceeds in three different ways: 1.ALPHA DECAY: The nucleus of an atom emits an alphaparticle which is composed of two protons and two neutrons.This loss changes the atomic mass number and also the
atomic number and a new element is produced, e.g., thedecay of Uranium-238 (U92 ) to Thorium-234 (Th90) in theUranium decay series. 2. BETA DECAY (ELECTRON LOSS):The neutron loses a high energy electron and thus convertedinto a proton. This loss changes only the atomic number butnot the atomic mass number, and hence new element isproduced, e.g., Rubidium-87 (Rb37) decay to Strontium-87(Sr38). 3. ELECTRON CAPTURE: is the opposite of betadecay as an electron is incorporated by a proton in thenucleus changing into neutron. This changes the atomicnumber only but not the atomic mass number, and hence anew element is produced e.g., Potassium-40 (K19) to Argon-40 (Aris).tha +2 D adioactive decay is expressed in terms of a length oftime called a HALF-LIFE. which is defined as the amount oftime necessary for half of the original parent atoms to decay

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Term
Spring
Professor
brooks

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