chemistry 25.2

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Chemistry 25.2

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Nuclear Transformations

Radon-222 is a radioactive isotope that is present naturally in the soil in some areas. It has a constant rate of decay. You will learn about decay rates of radioactive substances.

25.2

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Nuclear Transformations >

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Nuclear Stability and Decay

Nuclear Stability and Decay

What determines the type of decay a radioisotope undergoes?

25.2

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Nuclear Transformations > Nuclear Stability and Decay

• The nuclear force is an attractive force that acts between all nuclear particles that are extremely close together, such as protons and neutrons in a nucleus

• At these short distances, the nuclear force dominates over electromagnetic repulsions and hold the nucleus together.

25.2

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Nuclear Transformations > Nuclear Stability and Decay

More than 1,500 different nuclei are known. Of those, only 264 are stable and do not decay or change with time. These nuclei are in a region called the band of stability.

25.2

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Nuclear Transformations > Nuclear Stability and Decay25.2

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Nuclear Transformations > Nuclear Stability and Decay

The neutron-to-proton ratio determines the type of decay that occurs.

A positron is a particle with the mass of an electron but a positive charge. During positron emission, a proton changes to a neutron.

25.2

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Nuclear Transformations > Nuclear Stability and Decay25.2

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Nuclear Transformations >

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Half-Life

Half-Life

How much of a sample of a radioisotope remains after each half-life?

25.2

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Nuclear Transformations > Half-Life

A half-life (t1/2) is the time required for one-half of the nuclei of a radioisotope sample to decay to products.

After each half-life, half of the existing radioactive atoms have decayed into atoms of a new element.

25.2

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Nuclear Transformations > Half-Life25.2

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Nuclear Transformations > Half-Life25.2

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Nuclear Transformations > Half-Life

Simulation 30 Simulate the decay of several isotopes.

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Nuclear Transformations > Half-Life25.2

Stable Isotope

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Nuclear Transformations > Half-Life

The ratio of Carbon-14 to stable carbon in the remains of an organism changes in a predictable way that enables the archaeologist to obtain an estimate of its age.

25.2

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SAMPLE PROBLEM

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25.1

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SAMPLE PROBLEM

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25.1

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SAMPLE PROBLEM

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25.1

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SAMPLE PROBLEM

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25.1

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Practice Problems for Sample Problem 25.1

Problem Solving 25.7 Solve Problem 7 with the help of an interactive guided tutorial.

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Nuclear Transformations >

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Transmutation Reactions

Transmutation Reactions

What are two ways that transmutation can occur?

25.2

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Nuclear Transformations > Transmutation Reactions

The conversion of an atom of one element to an atom of another element is called transmutation.

Transmutation can occur by radioactive decay. Transmutation can also occur when particles bombard the nucleus of an atom.

25.2

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Nuclear Transformations > Transmutation Reactions

The first artificial transmutation reaction involved bombarding nitrogen gas with alpha particles.

25.2

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Nuclear Transformations > Transmutation Reactions

The elements in the periodic table with atomic numbers above 92, the atomic number of uranium, are called the transuranium elements.

• All transuranium elements undergo transmutation.

• None of the transuranium elements occur in nature, and all of them are radioactive.

25.2

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Nuclear Transformations > Transmutation Reactions

Transuranium elements are synthesized in nuclear reactors and nuclear accelerators.

25.2

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Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

25.2 Section Quiz.

25.2.

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25.2 Section Quiz.

1. During nuclear decay, if the atomic number decreases by one but the mass number is unchanged, the radiation emitted is

a. a positron.

b. an alpha particle.

c. a neutron.

d. a proton.

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25.2 Section Quiz.

2. When potassium-40 (atomic number 19) decays into calcium-40 (atomic number 20), the process can be described as

a. positron emission.

b. alpha emission.

c. beta emission.

d. electron capture.

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25.2 Section Quiz.

3. If there were 128 grams of radioactive material initially, what mass remains after four half-lives?

a. 4 grams

b. 32 grams

c. 16 grams

d. 8 grams

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25.2 Section Quiz.

4. When transmutation occurs, the ________ always changes.

a. number of electrons

b. mass number

c. atomic number

d. number of neutrons

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25.2 Section Quiz

5. Transmutation occurs by radioactive decay and also by

a. extreme heating.

b. chemical reaction.

c. high intensity electrical discharge.

d. particle bombardment of the nucleus.

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