unit 5: nuclear chemistry · introduction to radioactivity 2016 a.notebook 1 december 02, 2016 may...
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Introduction to Radioactivity 2016 A.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.
• Elements with atomic # 83 or greater are ALL unstable and radioactive. (Bismuth and up)
Introduction to Radioactivity 2016 A.notebook
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Radioactive Elements
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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
The radioactive particles can be found in reference Table O.
alpha Weakest penetrating power.
beta Moderate penetrating power, stronger than alpha.
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+
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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+
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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+
Introduction to Radioactivity 2016 A.notebook
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Gamma decay emission of energy in the form of a gamma particle. The mass number and atomic number remain the same.
Co60
270
0Co
60
27+