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Ch.21 - Radioactivity & Nuclear Chemistry
Tro - Chemistry: A Molecular Approach 6th Edition
Tro6th EditionChemistry: A Molecular ApproachISBN: 9780137832217Not the one you use?Change textbook
All textbooksTro 6th EditionCh.21 - Radioactivity & Nuclear ChemistryProblem 42a
Chapter 21, Problem 42a

Predict a likely mode of decay for each unstable nuclide. a. C-16

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Identify the atomic number and neutron number of the nuclide. For C-16, the atomic number (Z) is 6, and the mass number (A) is 16, so the number of neutrons is 16 - 6 = 10.
Determine the neutron-to-proton (n/p) ratio. For C-16, the n/p ratio is 10/6.
Compare the n/p ratio to the stable n/p ratio for light elements, which is approximately 1:1. C-16 has a higher n/p ratio than 1:1, indicating an excess of neutrons.
Consider the common decay modes for nuclides with excess neutrons. Beta decay (β⁻ decay) is a likely mode, where a neutron is converted into a proton, emitting a beta particle (electron) and an antineutrino.
Conclude that C-16 is likely to undergo beta decay to reduce its neutron-to-proton ratio, resulting in the formation of a more stable nuclide.

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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 energy released. Understanding the stability of a nuclide and the forces at play within the nucleus is essential for predicting its decay mode.
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Alpha Decay

Alpha Decay

Alpha decay is a type of radioactive decay in which an unstable nucleus emits an alpha particle, consisting of two protons and two neutrons. This process reduces the atomic number by two and the mass number by four, resulting in the formation of a new element. Alpha decay typically occurs in heavy nuclides, where the strong nuclear force is insufficient to hold the nucleus together.
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Beta Decay

Beta decay is a radioactive decay process where a neutron in an unstable nucleus is transformed into a proton, emitting a beta particle (an electron or positron) and an antineutrino or neutrino. This process increases the atomic number by one while keeping the mass number unchanged, leading to the formation of a different element. Beta decay is common in nuclides that have an excess of neutrons.
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Related Practice
Textbook Question

Predict a likely mode of decay for each unstable nuclide. b. Al-34

Textbook Question

Predict a likely mode of decay for each unstable nuclide. a. Ca-35

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

Which nuclide in each pair would you expect to have the longer half-life? a. Cs-149 or Cs-139 b. Fe-45 or Fe-52

Textbook Question

Predict a likely mode of decay for each unstable nuclide. c. In-132

Textbook Question

One of the nuclides in spent nuclear fuel is U-235, an alpha emitter with a half-life of 703 million years. How long will it take for the amount of U-235 to reach 10.0% of its initial amount?