1. Chapter 25 Nuclear Chemistry 25.1 Nuclear Radiation
25.2 Nuclear Transformations
25.3 Fission and Fusion
25.4 Radiation in Your Life
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2. What makes some types of radiation more dangerous than other types?
CHEMISTRY & YOU
What makes some types of radiation more dangerous than other types?
Lengthy or frequent exposure to X-rays can damage cells in your body.
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3. How do nuclear reactions differ from chemical reactions?
Radioactivity
Radioactivity
How do nuclear reactions differ from chemical reactions?
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4. Radioactivity
In 1896, the French chemist Antoine Becquerel made an accidental discovery.
He was studying the ability of uranium salts that had been exposed to sunlight to fog photographic film plates.
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5. Radioactivity
In 1896, the French chemist Antoine Becquerel made an accidental discovery.
He was studying the ability of uranium salts that had been exposed to sunlight to fog photographic film plates.
During bad weather, when Becquerel could not expose a sample to sunlight, he left the sample on top of the photographic plate.
When he developed the plate, he discovered that the uranium salt still fogged the film.
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6. Two of Becquerel’s associates were Marie and Pierre Curie.
Radioactivity
Two of Becquerel’s associates were Marie and Pierre Curie.
The Curies were able to show that rays emitted by uranium atoms caused the film to fog.
Marie Curie and her husband Pierre shared the
1903 Nobel Prize in physics with Becquerel for their pioneering work on radioactivity.
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7. Radioactivity
Marie Curie used the term radioactivity to refer to the spontaneous emission of rays or particles from certain elements, such as uranium.
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8. Radioactivity
Marie Curie used the term radioactivity to refer to the spontaneous emission of rays or particles from certain elements, such as uranium.
The rays and particles emitted from a radioactive source are called nuclear radiation.
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9. Radioactivity
Radioactivity, which is also called radioactive decay, is an example of a nuclear reaction.
Nuclear reactions begin with unstable isotopes, or radioisotopes.
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10. Radioactivity
Radioactivity, which is also called radioactive decay, is an example of a nuclear reaction.
Nuclear reactions begin with unstable isotopes, or radioisotopes.
Atoms of these isotopes become more stable when changes occur in their nuclei.
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11. Radioactivity
Radioactivity, which is also called radioactive decay, is an example of a nuclear reaction.
Nuclear reactions begin with unstable isotopes, or radioisotopes.
Atoms of these isotopes become more stable when changes occur in their nuclei.
The changes are always accompanied by the emission of large amounts of energy.
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12. Radioactivity
Unlike chemical reactions, nuclear reactions are not affected by changes in temperature, pressure, or the presence of catalysts. Also, nuclear reactions of a given radioisotope cannot be slowed down, sped up, or stopped.
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13. Radioactivity
Radioactive decay is a spontaneous process that does not require an input of energy.
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14. Radioactivity
Radioactive decay is a spontaneous process that does not require an input of energy.
If the product of a nuclear reaction is unstable, it will decay too.
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15. Radioactivity
Radioactive decay is a spontaneous process that does not require an input of energy.
If the product of a nuclear reaction is unstable, it will decay too.
The process continues until unstable isotopes of one element are changed, or transformed, into stable isotopes of a different element.
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16. Radioactivity
Radioactive decay is a spontaneous process that does not require an input of energy.
If the product of a nuclear reaction is unstable, it will decay too.
The process continues until unstable isotopes of one element are changed, or transformed, into stable isotopes of a different element.
These stable isotopes are not radioactive.
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17. Why do unstable isotopes undergo nuclear reactions?
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18. Why do unstable isotopes undergo nuclear reactions?
Unstable isotopes undergo nuclear reactions so that they may be changed, or transformed, into stable isotopes.
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19. What are three types of nuclear radiation?
Types of Radiation
Types of Radiation
What are three types of nuclear radiation?
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20. Radiation is emitted during radioactive decay.
Types of Radiation
Radiation is emitted during radioactive decay.
Three types of nuclear radiation are alpha radiation, beta radiation, and gamma radiation.
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21. Characteristics of Some Types of Radiation
Interpret Data
Characteristics of Some Types of Radiation
Type
Consists of
Symbol
Charge
Mass (amu)
Common source
Penetrating power
Alpha radiation
Alpha particles (helium nuclei) a, 2+ 4
Radium-226
Low (0.05 mm body tissue)
Beta radiation
Beta particles (electrons) b, 1–
1/1837
Carbon-14
Moderate
(4 mm body tissue)
Gamma radiation
High-energy electromagnetic radiation g
Cobalt-60
Very high (penetrates body easily) He 4 2 e –1
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22. Types of Radiation
Alpha Radiation
Some radioactive sources emit helium nuclei, which are also called alpha particles.
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23. Types of Radiation
Alpha Radiation
Some radioactive sources emit helium nuclei, which are also called alpha particles.
Each alpha particle contains two protons and two neutrons and has a double positive charge.
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24. Types of Radiation
Alpha Radiation
Some radioactive sources emit helium nuclei, which are also called alpha particles.
Each alpha particle contains two protons and two neutrons and has a double positive charge.
An alpha particle is written He or a. 4 2
The electric charge is usually omitted.
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25. Types of Radiation
Alpha Radiation
The radioisotope uranium-238 emits alpha radiation and is transformed into another radioisotope, thorium-234. U
238 92
Uranium-238
Th +
234 90
Thorium-234
He (a emission) 4 2
Alpha particle
Radioactive
decay
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26. Types of Radiation
Alpha Radiation
When an atom loses an alpha particle, the atomic number of the product is lowered by two and its mass number is lowered by four. U
238 92
Th +
234 90 He 4 2 →
In a balanced nuclear equation, the sum of the mass numbers (superscripts) on the right must equal the sum on the left.
The same is true for the atomic numbers (subscripts).
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27. Types of Radiation
Alpha Radiation
Because of their large mass and charge, alpha particles do not travel very far and are not very penetrating.
A sheet of paper or the surface of your skin can stop them.
But radioisotopes that emit alpha particles can cause harm when ingested.
Once inside the body, the particles don’t have to travel far to penetrate soft tissue.
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28. Types of Radiation
Beta Radiation
An electron resulting from the breaking apart of a neutron in an atom is called a beta particle.
The neutron breaks apart into a proton, which remains in the nucleus, and a fast-moving electron, which is released. n 1
Neutron
p +
Proton e –1
Electron
(beta particle) →
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29. Types of Radiation
Beta Radiation n 1
Neutron
p +
Proton e –1
Electron
(beta particle) →
The symbol for the electron has a subscript of –1 and a superscript of 0.
The –1 represents the charge on the electron.
The 0 represents the extremely small mass of the electron compared to the mass of a proton.
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30. Carbon-14 (radioactive)
Types of Radiation
Beta Radiation
Carbon-14 emits a beta particle as it decays and forms nitrogen-14. C 14 6
Carbon-14 (radioactive)
N + 7
Nitrogen-14 (stable)
e (b emission) –1
Beta particle →
The nitrogen-14 atom has the same mass number as carbon-14, but its atomic number has increased by 1.
It contains an additional proton and one fewer neutron.
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31. Types of Radiation
Beta Radiation
A beta particle has less charge than an alpha particle and much less mass than an alpha particle.
Thus, beta particles are more penetrating than alpha particles.
Beta particles can pass through paper but are stopped by aluminum foil or thin pieces of wood.
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32. Types of Radiation
Beta Radiation
Because of their opposite charges, alpha and beta radiation can be separated by an electric field.
Alpha particles move toward the negative plate.
Beta particles move toward the positive plate.
Gamma rays are not deflected.
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33. Types of Radiation
Gamma Radiation
A high-energy photon emitted by a radioisotope is called a gamma ray.
The high-energy photons are a form of electromagnetic radiation.
Nuclei often emit gamma rays along with alpha or beta particles during radioactive decay.
Ra +
226 88
Radium-226 Th
230 90
Thorium-230
He + g 4 2
Alpha particle
Gamma ray →
Pa +
234 91
Protactinium-234 Th 90
Thorium-234
e + g –1
Beta particle
Gamma ray →
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34. Gamma rays have no mass and no electrical charge.
Types of Radiation
Gamma Radiation
Gamma rays have no mass and no electrical charge.
Emission of gamma radiation does not alter the atomic number or mass number of an atom.
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35. Types of Radiation
Gamma Radiation
Because gamma rays are extremely penetrating, they can be very dangerous.
Gamma rays pass easily through paper, wood, and the human body.
They can be stopped, although not completely, by several meters of concrete or several centimeters of lead.
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36. CHEMISTRY & YOU
Gamma rays can be dangerous because of their penetrating power. What property determines the relative penetrating power of electromagnetic radiation?
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37. CHEMISTRY & YOU
Gamma rays can be dangerous because of their penetrating power. What property determines the relative penetrating power of electromagnetic radiation?
The wavelength and energy of electromagnetic radiation determine its relative penetrating power. Gamma rays have a shorter wavelength and higher energy than X-rays or visible light.
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38. Which process involves a radioactive nucleus releasing a high-speed electron?
A. oxidation
B. alpha emission
C. beta emission
D. gamma radiation
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39. Which process involves a radioactive nucleus releasing a high-speed electron?
A. oxidation
B. alpha emission
C. beta emission
D. gamma radiation
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40. Key Concepts
Unlike chemical reactions, nuclear reactions are not affected by changes in temperature, pressure, or the presence of catalysts. Also, nuclear reactions of a given radioisotope cannot be slowed down, sped up, or stopped.
Three types of nuclear radiation are alpha radiation, beta radiation, and gamma radiation.
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41. radioactivity: the process by which nuclei emit particles and rays
Glossary Terms
radioactivity: the process by which nuclei emit particles and rays
nuclear radiation: the penetrating rays and particles emitted by a radioactive source
radioisotope: an isotope that has an unstable nucleus and undergoes radioactive decay
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42. gamma ray: a high-energy photon emitted by a radioisotope
Glossary Terms
alpha particle: a positively charged particle emitted from certain radioactive nuclei; it consists of two protons and two neutrons and is identical to the nucleus of a helium atom
beta particle: an electron resulting from the breaking apart of neutrons in an atom
gamma ray: a high-energy photon emitted by a radioisotope
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43. Electrons and the Structure of Atoms
BIG IDEA
Electrons and the Structure of Atoms
Unstable atomic nuclei decay by emitting alpha or beta particles.
Often gamma rays are emitted too.
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44. END OF 25.1
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