Radioactive Isotope

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STUDY GUIDE ANSWERSThe Earth’s History Section 14-2 REVIEW

VOCABULARY REVIEW
radioactive isotope is an isotope whose nucleus tends to release particles, radiant energy, or both; radioactive dating is a technique for determining the age of a material by measuring the amount of a particular radioactive isotope the material contains.

radioactive decay is the release of particles, radiant energy, or both by a radioactive isotope half-life is the time it takes for one-half of any size sample of a particular isotope to decay.

microsphere is a spherical collection of many protein molecules organized as a membrane; coacervate is a collection of droplets that are composed of different types of molecules, including amino acids and sugars. Both structures are cell-like and form spontaneously in the laboratory from simple organic molecules.

MULTIPLE CHOICE
1. D The age of the Earth is estimated to be more than 4 billion years 2. C Sulfur has an atomic number of 16. The isotope sulfur-35 has 16 protons and 19 neutrons. 3. B When performing radioactive dating, scientists measure the amount of a particular radioactive isotope contained in a material.

4. A Carbon-14 dating is useful for estimating the age of relatively young organic material. 5. AResearchers using Miller/Urey have been able to produce amino acids and nucleotides.

SHORT ANSWER
1. Explain how the half-life of a radioactive isotope affects the usefulness of that isotope in dating specific types of rocks.
Isotopes with short half-lives are most useful for dating relatively young rocks, while those with long half-lives are most useful for dating older rocks.

2. Why do some scientists think that areas protected from the atmosphere might have favored the production of organic compounds on early Earth? Some scientists think that the atmosphere of early Earth contained large amounts of CO2, a gas that interferes with the...
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