Radioactivity and Decay 2018.notebook
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Unit 5: Nuclear Chemistry
Aim: Introduction to RadioactivityParticles and nuclear decay
Chapter 19 in textbookTopic 12 in review book
Reference Tables Used: Table N and Table O
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Element Stability
• Binding energyenergy that binds the nucleons of the nucleus together.
• 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.
Radioactivity and Decay 2018.notebook
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Radioactive Elements• Elements with atomic # 83 or greater are unstable and only exist as radioisotopes (Bismuth and up).
• Radioisotope: radioactive isotope of an element.
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What is Radioactivity?Unstable nuclei are radioactive and will undergo natural transmutation.
• 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
beta Moderate stronger than alpha. weaker than gamma
gamma Strongest penetrating power of all particles.
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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 2018.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
55e0
1Ni137
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: