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Radioactivity and Decay 2017.notebook
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Unit 5: Nuclear Chemistry
Aim: Introduction to RadioactivityParticles and decay
Chapter 19 in textbookTables Used: Table N and Table O
https://phet.colorado.edu/sims/html/buildanatom/latest/buildanatom_en.html
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Element Stability• Stable nuclei of elements have a proton to neutron ratio of 1:1 or close to it.
• Unstable nuclei of elements have a larger p to n ratio than 1:1> The protons and neutrons exist in a balance that stabilizes the nuclear force and binding energy.
• Binding energyenergy that binds the nucleons of the nucleus together.
Radioactivity and Decay 2017.notebook
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Radioactive Elements• Elements with atomic # 83 or greater are ALL unstable and radioactive. (Bismuth and up)
• Elements with an atomic # of 83 or greater exist only as radioisotopes.
• Radioisotope: radioactive isotope of an element.
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What is Radioactivity?
Unstable nuclei are radioactive and will undergo natural transmutation (radioactive decay).
• Natural transmutation: when an unstable nucleus spontaneously decays and mutates to become more stable.
238U 4He + 234Th92 2 90
• Uranium238 nucleus is unstable and will decay by releasing an alpha particle (Table N decay mode) and transmutates into Thorium234.
Mass # Mass #
Charge Charge
• The mass number and charge are conserved. (equal on both sides of the nuclear equation).
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Radioactive Particles
Name Symbol Strength (penetrating power)
The radioactive particles can be found in reference Table O.
alpha Weakest penetrating power. Stopped by a piece of paper.
beta Moderate penetrating power, stronger than alpha. Stopped by thick pieces of glass.
gamma Strongest penetrating power of all particles. Stopped by 6 ft of concrete or thickpieces of lead.
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Alpha decay the emission of an alpha particle by the nucleus. The mass decreases by 4 and the atomic number decreases by 2.
Pu240
94 He4
2 U236
92+Equation:
Radioactivity and Decay 2017.notebook
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Beta decay (β): the emission of an electron. The atomic number increases by 1 and mass number remains the same.
Co137
55e
0
1Ni
137
56+Equation:
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Positron decay (β+): the nucleus gives off a positron. The atomic number decreases by 1 and the mass remains the same.
Na22
11 e0+1 Ne
22
10+Equation:
Radioactivity and Decay 2017.notebook
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Gamma decay emission of pure energy in the form of a gamma particle. The mass number and atomic number remain the same.
Co60
270
0Co
60
27+Equation:
