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Nuclear Chemistry. Chad Van Every. Radioisotopes. A radioisotope is a radioactive isotope of an element. Ex: A natural radioisotope of Uranium-238 is Uranium-235 Radioisotopes are constantly decaying into other elements.
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Nuclear Chemistry Chad Van Every
Radioisotopes • A radioisotope is a radioactive isotope of an element. • Ex: A natural radioisotope of Uranium-238 is Uranium-235 • Radioisotopes are constantly decaying into other elements. • The half-life of a radioactive isotope is the time it takes for one half of a sample of that isotope to decay. • Question: If you have 8 grams of an element and its half-life is 1 day, how many grams are left after 3 days?
Radioisotopes • - Carbon-14 is a well known radioactive isotope that is used in radiocarbon dating. • - It has a half-life of 5730 years. • Based on its half-life, scientists can determine the age of plant, animal, and object remains. -Note: this works up to 30,000 years
Radioisotopes • One way to make a stable nucleus unstable is with a nuclear bombardment reaction. • An atom is bombarded with a stream of particles such as alpha (α) particles, forming a new nucleus • Ex: α + N → O + H
Biological Effects of Radiation • The SI unit of radioactivity is the becquerel, named after Henri Becquerel. • A more widely used unit is the curie (Ci), named after Pierre and Marie Curie. • The rem (roentgen equivalent for man) measures radiation exposure in humans.
Biological Effects of Radiation • A dosimeter measures the total amount of radiation that a person has received. • A Geiger counter detects radiation. • High energy radiation (such as gamma) forms free radicals inside the body and can destroy tissue. • NOTE: Radiation damage may affect an organism directly or it may affect the organism’s offspring, if reproductive cells are affected.
Biological Effects of Radiation • In spite of the hazards of radiation, radioisotopes are very beneficial in medicine, agriculture, and industry. • --- Radiotracers use radioactive substances to follow a specified substance as it moves through a natural system. • --- Radiotherapy uses radioactive substances to help treat cancer. • --- Radiation can be used to help preserve foods such as strawberries.
Harnessing the Nucleus • In a nuclear fission reaction, a large nucleus is split into two smaller nuclei of approximately equal mass. • Ex: n + U → U → Ba + Kr + 3n • ***Mass and charge are conserved*** • Ex: atomic bomb • Massive amounts of energy are released and can be calculated by the equation: E = • When one fission reaction occurs, many more follow behind the first, creating a chain reaction.
Harnessing the Nucleus • Nuclear reactors are not able to explode like an atomic bomb because they are regulated by control rods that slow down the speed of the neutrons.
Harnessing the Nucleus • In a nuclear fusion reaction, two small nuclei join to form a large nucleus. • Ex: H + H → He + n • ***Mass and charge are conserved*** • Ex: the sun • Fusion reactions are still in the experimental stage because they are very difficult to create and control.
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