Radioactivity and Nuclear Energy
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Transcript of Radioactivity and Nuclear Energy
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Radioactivity and Nuclear EnergyChapter 19
http://www.youtube.com/watch?v=PEHcHcneFFc&feature=related
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Chemical vs. Nuclear
Chemical Reactions
• Break and form bonds
• Created with valence electrons
• Type of elements do not change during the reaction
• Small energy changes
Nuclear Reactions• Involve nuclei
changes• Can involve e-, p+,
and no
• Convert 1 element to another element
• LARGE energy changes
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Facts about the Nucleus
•The nucleus is composed of nucleons:
–Neutrons and protons
U23592
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Isotopes and Nuclides
•Isotopes: atoms that have identical atomic numbers but different mass numbers
CCC 146
136
126
How are they similar? How are they different?
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Radioactivity
• Radioactivity – the result of the spontaneous decomposition of an unstable nucleus. – Includes the production of high energy
particles that make the nucleus more stable.
e N C 01-
147
146
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Radioactive Isotopes
•85% of the 2000 known isotopes are radioactive.
–279 of those 2000 are not radioactive
•Percent abundance of isotopes is much smaller.
–Not radioactive: C-12 – 99% of all C–Radioactive: C-14 < 0.1%
85%
15%
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How do we know if a nucleus is stable?
– Protons and neutrons are nucleons
– Held together by strong nuclear force
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Nuclear Stability•How can you tell if an element is stable?
–Look at proton to neutron ratio (p:n)
–Atomic number less than 20:• Want p:n = 1:1
–Above atomic number 20 have more neutrons than protons, which increases the ratio
ON, C, 168
147
126
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Where are the stable nuclei found?
•Band of Stability shows where the stable nuclei can be found
– Depends on the proton to neutron ratio
– Location determines the type of decay for the isotope
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How can I become a stable nucleus?1. Alpha Radiation
–Helium nuclei are emitted from a radioactive source
•Called alpha particles–Contain two protons and two neutrons
»Overall positive charge
U
Th
He
He42
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How can I become a stable nucleus?
2. Beta Radiation–Fast-moving electrons created by the break-down of a neutron in an atom
•Called beta particles
e01-
C
N
e-
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How can I become a stable nucleus?
3. Gamma Radiation–High-energy electromagnetic radiation given off by a radioisotope
•Often given-off along with alpha or beta radiation
–Have no mass or charge
00
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How can I become a stable nucleus?4. positron emission
–Positron :•has same mass as an electron but the opposite charge
•Created when a proton breaks apart to create a neutron and positron
e01
B
Be
e+
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How can I become a stable nucleus?5. Electron capture
•Capture an inner electron and turn it into a proton
•“Hand of God”
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Practice time
• Practice WS with isotopic notation and what ratio you have for Neutron to proton and types of decay – due tomorrow!!!