chap21notes - AP Chemistry Chapter 21 - The Nucleus: A...

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1 AP Chemistry Chapter 21 - The Nucleus: A Chemist’s View 21.1 Nuclear Stability and Radioactive Decay A. Radioactive Decay 1. Decomposition forming a different nucleus and producing one or more particles a. Total mass number and atomic number must be conserved in any nuclear change n C He Be 1 0 12 6 4 2 9 4 + + B. Zone of Stability 1. Of 2000 known nuclides, only 279 are stable with respect to radioactive decay 2. All nuclides with more than 83 protons (bismuth) are unstable 3. Light nuclides are most stable when the neutron/proton ratio is 1 4. Heavier nuclides are most stable when the neutron/proton ratio is greater than 1 5. Magic numbers a. Special stability exists when the number of protons or neutrons is: 2, 8, 20, 28, 50, 82, 126 C. Types of Radioactive Decay 1. Alpha Emission a. Alpha particle ( α ) is a helium nucleus ( He 4 2 ), so it has a 2+ charge b. Alpha emission is restricted almost entirely to very heavy nuclei He Pb Po 4 2 206 82 210 84 + + 2. Beta Emission a. Beta particle ( β ) is an electron emitted from the nucleus during nuclear decay b 0 1 1 1 1 0 - + p n b. Beta particles are emitted when a neutron is converted into a proton and an electron b 0 1 14 7 14 6 - + N C 3. Positron Emission a. Positrons are particles that have the same mass as an electron, but a positive charge b. Positron emission arises from the conversion of a proton into a neutron and a positron b 0 1 1 0 1 1 + + n p b 0 1 38 18 38 19 + + Ar K
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2 4. Electron Capture a. Inner orbital electron is captured by the nucleus of its own atom
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This note was uploaded on 09/28/2009 for the course CHEM 102 taught by Professor Freeman during the Spring '08 term at South Carolina.

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chap21notes - AP Chemistry Chapter 21 - The Nucleus: A...

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