Understanding Radioactivity Lesson 8 PDF
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Uploaded by MerryKnowledge
BIU
2025
Solav Salih
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Summary
This lesson describes radioactivity, including its types, properties, and medical applications. It also explains half-life and radiocarbon dating. The document is part of the Chemistry Module - Medicine (Pathway Programme) 2024-2025.
Full Transcript
UNDERSTANDING RADIOACTIVITY By Solav Salih Chemistry Module - Medicine (Pathway Programme) 2024-2025 LEARNING OBJECTIVES At the end of the lesson, you will learn about: Radioactivity, Radioactive Nuclear its types and Decay, Half- energy and their Life and...
UNDERSTANDING RADIOACTIVITY By Solav Salih Chemistry Module - Medicine (Pathway Programme) 2024-2025 LEARNING OBJECTIVES At the end of the lesson, you will learn about: Radioactivity, Radioactive Nuclear its types and Decay, Half- energy and their Life and its medical properties radiocarbon application dating Discovery of Radioactivity 1896 1898 Henri Becquerel Marie Curie RADIOACTIVITY Radioactive decay is the process by which an unstable atomic nucleus loses energy by radiation. This process occurs in a nucleus that is unstable and hence radioactive. Natural radiation emitted by unstable nuclei includes alpha particles, beta particles, Nuclear symbol: positrons, and gamma rays. or 99.9% Fluorine-19 ALPHA PARTICLES An alpha particle (α) contains two protons or or and two neutrons, identical to the nucleus of the helium atom. It has no electrons to counterbalance the nuclear charge (charge = +2) Relatively large mass, slow-moving particles (10% of the speed of light) Can be stopped by barriers as thin as a few papers BETA PARTICLES The beta particle (β) is a fast-moving electron (90% of the speed of light) It is formed in the nucleus by the conversion of a neutron into a proton Beta particles are smaller, faster and more penetrating than alpha particles Can be stopped by wood, metal, or several layers of clothing. or or POSITRONS Has the same mass as a beta particle but carries a positive charge Is symbolized as The proton loses its positive charge, as well as a tiny bit of mass. This positively charged mass that is released is the Produced by the conversion of a positron. proton to a neutron in the nucleus of the isotope. GAMMA RAYS The most energetic part of the electromagnetic spectrum In contrast to alpha and beta radiation which have both energy and mass - gamma rays are purely energy Most penetrating form of nuclear radiation. Stopped by lead or concrete. PROPERTIES SUMMARY Ionizing radiation produces a trail of ions throughout the material that it penetrates. The ionization process changes the chemical composition of the material. When the material is living tissue, radiation-induced illness may result Damage to internal Cause skin can damage organs is negligible and eye internal organs except when ingested damage NUCLEAR EQUATION Nuclear equations represent nuclear change in much the same way as chemical equations represent chemical change. If gamma radiation were the only product of nuclear decay, there would be no measurable change in the mass or identity of the radioactive nuclei. PREDICTING NUCLEAR EQUATIONS 1. 2. 3. HALF LIFE ( ) It is the time required for one-half of a given quantity of the radioactive isotope to undergo change (decay) Each isotope has its own characteristic half-life that may be as short as a few millionths of a second or as long as billions of years Isotopes with short half-lives decay rapidly; they are very unstable EXTENT OF RADIOACTIVE DECAY The mass of any radioactive substance remaining after a period may be calculated with a knowledge of the initial mass and the half-life of the isotope: E.g.: PREDICTING EXTENT OF DECAY A 50.0-mg supply of iodine-131, used in hospitals in the treatment of hyperthyroidism, was stored for 32.4 days. If the half-life of iodine-131 is 8.1 days, how many mg remain? RADIOCARBON DATING Radiocarbon dating is the estimation of the age of objects through measurement of isotopic ratios of carbon Useful in establishing the approximate age of objects of archaeological, anthropological, or historical interest Based on the measurement of ratio of Carbon-14 and Carbon-12 present in an object. RADIOCARBON DATING-CONT. Carbon-14 is formed in the upper atmosphere by the bombardment of Nitrogen-14 by high-speed neutrons (cosmic radiation): Carbon-14 and Carbon-12 are converted into living plant material by photosynthesis, which is later consumed by animals (including humans) The amount of carbon-14 slowly decreases because carbon-14 is radioactive (half-life is 5730 years): By using suitable equations involving the relative amounts of carbon-14 and carbon-12, it is possible to approximate the age of the artifact. This technique has been widely used to increase our knowledge about the history of the earth, to establish the age of objects, and even to detect art forgeries. The carbon-14 dating technique is limited to objects that are