Nuclear Chemistry Chapter 5

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Questions and Answers

What is the outcome of an alpha decay?

The atomic number remains unchanged.

The mass number decreases by 4. (correct)

The atomic number decreases by 4.

The mass number increases by 2.

In a balanced nuclear equation, how must the mass numbers on each side relate?

They must only be less than or equal to each other.

They must be equal. (correct)

They must add up to a prime number.

They can differ by any value.

Which type of radiation is emitted during alpha decay?

Alpha particle. (correct)

Proton.

Gamma rays.

Neutron.

What happens to the atomic number of a nucleus undergoing alpha decay?

It decreases by 2. Signup and view all the answers

Which of the following best represents a nuclear equation for alpha decay?

Uranium-238 → Thorium-234 + Alpha particle Signup and view all the answers

What represents the atomic symbol for an alpha particle?

He Signup and view all the answers

Which scenario describes a nucleus that has undergone radioactive decay?

A nucleus emits radiation and changes to a different element. Signup and view all the answers

For the decay of americium-241, what would the completed nuclear equation indicate?

A new nucleus with a mass number of 237 is formed. Signup and view all the answers

What is the atomic symbol for the new nucleus formed after the beta decay of cobalt-60?

Ni Signup and view all the answers

In the beta decay of cobalt-60, what is the change in atomic number?

It decreases by 1 Signup and view all the answers

What substance is commonly used in thyroid scans to assess radioactivity in the thyroid?

Iodine-131 Signup and view all the answers

What type of imagery does positron emission tomography (PET) produce?

Three-dimensional images Signup and view all the answers

What is the mass number of the new nucleus after the beta decay of cobalt-60?

60 Signup and view all the answers

Which of the following radioisotopes is NOT mentioned as a positron emitter in PET scans?

Nitrogen-14 Signup and view all the answers

What element has an atomic number of 40 and is related to beta decay examples?

Zirconium Signup and view all the answers

What particle is emitted during the beta decay process?

Positron Signup and view all the answers

What is the main function of the gamma rays emitted from radioisotopes during scans?

To expose a photographic plate Signup and view all the answers

In PET scans, positrons emitted from radioisotopes combine with what particle to produce gamma rays?

Electrons Signup and view all the answers

Which of the following statements regarding positron emission is true?

Mass number remains the same Signup and view all the answers

What does a radioactive thyroid scan typically indicate about organ function?

Accumulation of radioactivity in the organ Signup and view all the answers

What would be the atomic number of cobalt-60 before decay?

27 Signup and view all the answers

What type of substances are positron emitters combined with in PET to study brain activity?

Body substances like glucose Signup and view all the answers

Which process describes the conversion of a proton into a neutron?

Beta decay Signup and view all the answers

What feature distinguishes radioisotope scans from other imaging techniques?

Detection of emitted radiation Signup and view all the answers

What is the remaining amount of I-123 after 26.4 hours from a 64-mg sample?

16 mg Signup and view all the answers

How many half-lives have passed after 26.4 hours for I-123?

2 half-lives Signup and view all the answers

If 64 mg of I-123 reduces to 4.0 mg, how many half-lives have passed?

4 half-lives Signup and view all the answers

What is the half-life of I-123?

13.2 hours Signup and view all the answers

After how many half-lives will a substance reach approximately 80% decay?

3 half-lives Signup and view all the answers

How much of a 64 mg sample of I-123 remains after one half-life?

32 mg Signup and view all the answers

If the half-life were to double, what would be the new half-life of I-123?

26.4 hours Signup and view all the answers

What fraction of the original sample remains after 2 half-lives?

1/4 Signup and view all the answers

What occurs during nuclear fission?

A large nucleus splits into smaller nuclei and neutrons Signup and view all the answers

What happens when a neutron bombards U-235?

U-236 is formed and undergoes fission Signup and view all the answers

What is the significance of the equation E = mc² in nuclear fission?

It shows that mass and energy are equivalent Signup and view all the answers

What characterizes a nuclear chain reaction?

It requires a critical mass of uranium to sustain the reaction Signup and view all the answers

What is produced as a result of uranium-235 undergoing fission?

Three neutrons and new lighter elements like Kr-91 and Ba-142 Signup and view all the answers

What is meant by 'critical mass' in the context of nuclear fission?

The amount of fissionable material needed to maintain a chain reaction Signup and view all the answers

Which of the following statements about the neutrons emitted during fission is correct?

They can cause additional fission events in U-235 nuclei Signup and view all the answers

How is energy released in nuclear fission?

From the conversion of missing mass into energy Signup and view all the answers

Which process is characterized by the combination of small nuclei to form larger nuclei?

Nuclear fusion Signup and view all the answers

What is the primary energy source used in nuclear power plants to generate electricity?

Nuclear fission Signup and view all the answers

At what temperature does nuclear fusion typically occur?

100,000,000 °C Signup and view all the answers

Which of the following statements about nuclear fusion is true?

It combines hydrogen isotopes to form helium. Signup and view all the answers

How does the waste production of nuclear fusion compare to nuclear fission?

Fusion produces less waste. Signup and view all the answers

In a nuclear fission process, what role do control rods play?

They absorb neutrons to slow down the reaction. Signup and view all the answers

What percentage of electricity in the United States is supplied by nuclear power plants?

20% Signup and view all the answers

Which of the following is NOT a characteristic of nuclear fusion?

Involves splitting large nuclei. Signup and view all the answers

Study Notes

Chapter 5: Nuclear Chemistry

Nuclear chemistry examines unstable nuclei that spontaneously emit particles and energy to become more stable.
Most isotopes of elements with atomic numbers 19 or lower are stable.
Elements 20 and higher typically have some radioactive isotopes due to strong proton repulsions.
Radioactive isotopes are unstable nuclei that emit radiation.
Radioisotopes can be one or more isotopes of an element and are identified by mass number (protons + neutrons).
Examples of radioisotopes include Carbon-14 (used in archeological dating, mass #14, atomic #6).

Types of Radiation

Alpha (α) particles: identical to a helium nucleus (He-4), have 2 protons and 2 neutrons, +2 charge, low energy, stopped by paper or clothing.
Beta (β) particles: high-energy electrons, -1 charge, mass #0, stopped by heavy clothing or lab coats, and aluminum
Positrons (β+): high-energy particles, identical to electrons but with a +1 charge, mass #0, stopped by heavy clothing, and aluminum.
Gamma (γ) rays: pure energy, no mass or charge, very high-energy radiation, penetrates thick materials like concrete or lead.

Radiation Protection

Alpha particles require paper and clothing.
Beta particles require lab coats or gloves.
Gamma rays require lead or thick concrete.
Limiting time near a radioactive source.
Increasing distance from the source.
Shielding material varies in effectiveness based on the type of radiation.

Nuclear Reactions

Nuclear equations show changes in nuclear reactions using atomic symbols.
Mass and atomic numbers are conserved in nuclear equations.

Radioactive Decay

Radioactive decay is a process where an unstable nucleus breaks down by emitting radiation.
The decay is described by a nuclear equation showing the radioactive nucleus, new nucleus, and radiation emitted (α, β, β+, γ).

Units of Radiation Measurement

Curie (Ci): the number of disintegrations per second for 1 gram of radium.
Becquerel (Bq): the SI unit of activity (1 disintegration per second).
Rad (radiation absorbed dose): measures the amount of radiation absorbed by a gram of material.
Rem (radiation equivalent in humans): measures the biological effects of different kinds of radiation on humans.
Conversion factors exist to account for the different penetration power and biological effects of different types of radiation.

Radiation Exposure

The average person in the US is annually exposed to 3.6 mSv of radiation.
Natural sources (buildings, food, water).
Medical sources (X-rays, mammograms)
High levels of radiation exposure can cause radiation sickness.
Lethal doses exist for different life forms.

Medical Applications Using Radioactivity

Different radioisotopes with short half-lives are utilized to diagnose and treat diseases.
Body cells do not discriminate between radioactive and normal atoms.
The emitted radiation from the radioisotope is used to produce images of the organ.
Different organs and diseases can be identified by different isotopes.
Examples of radioisotopes include I-131 for thyroid, Ga-68 for pancreas, and Tc-99m for brain/bone scans.

Radiological Dating

Radiological dating is a technique used by geologists, archaeologists, and historians to determine the age of ancient objects.
It is determined by measuring the amount of Carbon-14, a radioactive isotope, present.
The uptake of carbon-14 in CO₂ stops when the plant dies.
As carbon-14 decays, the amount of radioactive carbon decreases.
Half-life of carbon-14 is used to calculate the time since the plant died

Nuclear Fission and Fusion

Fission: A large nucleus is bombarded with particles (e.g., neutron), causing it to split into smaller nuclei and releasing a large amount of energy.
Fusion: Small nuclei combine to form a larger nucleus, releasing a large amount of energy at extremely high temperatures (e.g., Sun and stars).
Nuclear power plants use fission to generate electricity.

Nuclear Power Plants

Nuclear fission in power plants utilizes controlled processes of U-235 to produce energy.
Critical mass is kept below the critical value to control the process.

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Description

Explore the fascinating world of Nuclear Chemistry in this Chapter 5 quiz. Learn about unstable nuclei, types of radiation, and the characteristics of various isotopes. This quiz will test your knowledge on topics such as radioactive isotopes and their applications.