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CHAPTER 25 – NUCLEAR CHEMISTRY Radioactivity – process by which Uranium gives off rays Radioisotopes – radioactive isotopes; because they are unstable **Why do radioisotopes undergo radioactive decay??? Types of radioactive decay: 1.) Alpha 2.) Beta 3.) Gamma Nuclear Stability Plot: Ratio of Neutrons to Protons **Stable Nuclei do not decay or change over time!!! Half-Life – Time required for one-half of the atoms of a radioisotope to emit radiation and to decay to products **Can anyone think of a use for a radioisotope with a short half-life? Long half-life? Example: Nitrogen -13 emits beta radiation and decays to carbon-13 with a t1\2= 10 minutes. Assume a starting mass of 2.00g of Nitrogen. a.) How long is four half-lives? One half-life is equal to 10 minutes. Four half-lives is 4 x 10 min = 40 minutes b.) How many grams of Nitrogen-13 will still exist after three halflives? Number of half-lives 0 1 2 3 Mass (g) 2.00 1.00 0.50 0.25 Time (min) 0 10 20 30 **Math challenge: Is there an equation you could use to find the same answer above?? Initial Mass (1\2)x where x = number of half-lives Transmutation Reactions – Conversion of an atom of one element to an atom of another element. Transuranium Elements- All elements above atomic number 92 all undergo transmutation and do not occur naturally. Nuclear Fission versus Fusion Fission – When the nuclei of certain isotopes are bombarded with neutrons the nucleus splits. Ex- Nuclear Reactors; Atomic Bombs Fusion – When two nuclei combine to produce a nucleus of heavier mass; releases more energy than fission. Ex.- Solar Fusion