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Isotopes & Radioactivity
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Isotopes of Magnesium Atomic symbol Mg Mg Mg Number of protons12 12 12 Number of electrons12 12 12 Mass number 24 25 26 Number of neutrons 12 13 14 24 12 25 12 26 12 Isotope Notation Mg-24 Mg-25 Mg-26 Timberlake, Chemistry 7 th Edition, page 64 12p + 12n 0 12p + 13n 0 12p + 14n 0 12e -
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Isotopes of Hydrogen 1 p + 1 e - 1 p + 1 n 1 e - 1 p+ 2 n 1 e - ProtiumDeuteriumTritium (ordinary hydrogen) (heavy hydrogen)(radioactive hydrogen) Ralph A. Burns, Fundamentals of Chemistry 1999, page 100 H-2H-3H-1
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Isotopes of Hydrogen ProtiumProtium (H-1) 1 proton, 0 neutrons, 1 electron most abundant isotope DeuteriumDeuterium (H-2) 1 proton, 1 neutron, 1 electron used in “heavy water” TritiumTritium (H-3) 1 proton, 2 neutrons, 1 electron radioactive 1 p + 1 e - 1 p + 1 n 1 e - 1 p+ 2 n 1 e -
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Isotopes of Three Common Elements ElementSymbol Fractional Abundance Average Atomic Mass Carbon Chlorine Silicon Si 28 29 30 27.977 28.976 29.974 92.21% 4.70% 3.09% 12 6 13 6 35 17 37 17 28 14 29 14 30 14 12.01 35.45 28.09 1.11%13.003 13 C 98.89% 12 (exactly)12 C Mass (amu) 75.53% 24.47%36.96637Cl 34.96935Cl Mass Number LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World, 1996, page 110
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Radioactivity (1896) 1. rays or particles produced by unstable nuclei a. Alpha Rays – helium nucleus b. Beta Part. – high speed electron c. Gamma ray – high energy x-ray 2. Discovered by Becquerel – exposed photographic film 3. Further work by Curies Antoine-Henri Becquerel (1852 - 1908)
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Radioactivity Marie CurieOne of the pieces of evidence for the fact that atoms are made of smaller particles came from the work of Marie Curie (1876 - 1934). She discovered radioactivity, the spontaneous disintegration of some elements into smaller pieces.
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Radioisotopes Radioactive isotopes Many uses –Medical diagnostics –Optimal composition of fertilizers –Abrasion studies in engines and tires Radioisotope is injected into the bloodstream to observe circulation.
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Half-Life of Isotopes Isotope Half-Life Radiation emitted Half-Lives and Radiation of Some Naturally Occurring Radioisotopes Carbon-14 5.73 x 10 3 years Potassium-40 1.25 x 10 9 years Thorium-234 24.1 days Radon-2223.8 days Radium-2261.6 x 10 3 years Thorium-230 7.54 x 10 4 years Uranium-235 7.0 x 10 8 years Uranium-2384.46 x 10 9 years
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Atomic Structure Review ATOMSATOMS –Differ by number of protons IONSIONS –Differ by number of electrons ISOTOPESISOTOPES –Differ by number of neutrons
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