Ch.20 - Radioactivity and Nuclear Chemistry

Problem 41a

Chapter 20, Problem 41a

Predict a likely mode of decay for each unstable nuclide. a. Mo-109

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Identify the atomic number of molybdenum (Mo), which is 42.

Determine the neutron number by subtracting the atomic number from the mass number: 109 - 42.

Compare the neutron-to-proton ratio of Mo-109 to the stable isotopes of molybdenum to assess its stability.

Consider common decay modes: beta decay, alpha decay, and positron emission/electron capture, and determine which is likely based on the neutron-to-proton ratio.

Conclude that if the neutron-to-proton ratio is high, beta decay is likely, as it converts a neutron to a proton, reducing the ratio.

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Key Concepts

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

Nuclear Decay

Nuclear decay refers to the process by which an unstable atomic nucleus loses energy by emitting radiation. This can occur through various modes, including alpha decay, beta decay, and gamma decay, each characterized by the type of particle or radiation emitted. Understanding the stability of nuclides and the forces at play within the nucleus is essential for predicting the mode of decay.

Isotopes and Stability

Isotopes are variants of a chemical element that have the same number of protons but different numbers of neutrons. The stability of an isotope depends on the ratio of neutrons to protons; an imbalance can lead to instability and subsequent decay. For example, Mo-109 has a specific neutron-to-proton ratio that influences its decay mode, making it crucial to analyze isotopes when predicting decay.

Decay Chains

Decay chains are sequences of decays that occur when a radioactive nuclide transforms into a series of other nuclides until a stable one is reached. Each step in the chain can involve different decay modes, and understanding these chains helps in predicting the behavior of nuclides like Mo-109. Recognizing the end products and intermediate nuclides is vital for a comprehensive understanding of nuclear decay processes.

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Related Practice

Textbook Question

Determine whether or not each nuclide is likely to be stable. State your reasons. d. Te-124

Textbook Question

Determine whether or not each nuclide is likely to be stable. State your reasons. a. Ti-48 b. Cr-63 c. Sn-102 d. Y-88

Textbook Question

The first six elements of the first transition series have the following number of stable isotopes:

Element Number of Stable Isotopes

Sc 1

Ti 5

V 1

Cr 3

Mn 1

Fe 4

Explain why Sc, V, and Mn each have only one stable isotope while the other elements have several.

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Textbook Question

Predict a likely mode of decay for each unstable nuclide. b. Ru-90 c. P-27 d. Sn-100

Textbook Question

Predict a likely mode of decay for each unstable nuclide. a. Sb-132 b. Te-139 d. Ba-123

Textbook Question

Predict a likely mode of decay for each unstable nuclide. c. Fr-202