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Ch.21 - Nuclear Chemistry
Chapter 21, Problem 5a

The steps below show three of the steps in the radioactive decay chain for 23290Th. The half-life of each isotope is shown below the symbol of the isotope. (a) Identify the type of radioactive decay for each of the steps (i), (ii), and (iii). [Sections 21.2 and 21.4]


Diagram showing radioactive decay steps for 23290Th with half-lives for each isotope.

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1
Step 1: Identify the initial isotope and its decay product for step (i). The initial isotope is ^{232}_{90}Th and the decay product is ^{228}_{88}Rn.
Step 2: Determine the type of decay for step (i). Since the atomic number decreases by 2 and the mass number decreases by 4, this indicates an alpha decay.
Step 3: Identify the initial isotope and its decay product for step (ii). The initial isotope is ^{228}_{88}Rn and the decay product is ^{228}_{89}Ac.
Step 4: Determine the type of decay for step (ii). Since the atomic number increases by 1 and the mass number remains the same, this indicates a beta decay.
Step 5: Identify the initial isotope and its decay product for step (iii). The initial isotope is ^{228}_{89}Ac and the decay product is ^{228}_{90}Th. Determine the type of decay for step (iii). Since the atomic number increases by 1 and the mass number remains the same, this indicates a beta decay.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Radioactive Decay

Radioactive decay is the process by which unstable atomic nuclei lose energy by emitting radiation. This decay can occur in various forms, including alpha decay, beta decay, and gamma decay, each involving the transformation of the nucleus and the release of particles or electromagnetic radiation. Understanding the type of decay is crucial for predicting the behavior of radioactive isotopes over time.
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Rate of Radioactive Decay

Half-Life

The half-life of a radioactive isotope is the time required for half of the radioactive atoms in a sample to decay. This concept is fundamental in nuclear chemistry as it helps in determining the stability of isotopes and the rate at which they decay. Each isotope has a unique half-life, which can range from fractions of a second to billions of years, influencing its applications in fields like dating and medical treatments.
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Decay Chain

A decay chain, or radioactive series, is a sequence of decays that a radioactive isotope undergoes until it reaches a stable end product. Each step in the chain involves the transformation of one isotope into another, often with different half-lives and decay types. Understanding decay chains is essential for predicting the behavior of radioactive materials and their potential impacts on health and the environment.
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