Chem 102 1st Edition Lecture 21Outline of Last Lecture I. Complex ColorII. Crystal Field Theory A. OctahedralB. TetrahedralC. Square PlanarOutline of Current LectureI. Nuclear ChemistryII. Radioactive Decay ReactionsIII. Nuclide StabilityIV. Nuclear TransmutationV. Radioactive DecayCurrent LectureI. Nuclear Chemistry- Study of nuclear reactions with emphasis on uses in chemistry and effect on biological systems. Nuclear reactions involve changes in nucleus, generating energy. -Nucleons- particles inside the nucleus, protons and neutrons. Atomic number, Z is the number of protons in an atom. Mass number is the number of protons and nuetrons. -Isotopes- The same atom with same protons but different nuetrons. -Normal Chemical reactions involve the transfer of electrons. Same elements are on both sides of the equation. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-Nuclear reactions involve the gain, or loss of nucleons. Different elements on each side of equation. Unstable radionuclides will spontaneously emit particles and electromagnetic radiation. Unstable nucleus transforms into a more stable but less energetic nucleus. II. Radioactive Decay Reactions- Alpha emission- gives off 42 He. Beta emission- gives off electron, atomic # increases. Positron emission- proton converts to a neutron. Electroncapture- takes in an electron.III. Nuclide Stability- Nuclei with even protons, neutrons or both are more likely to be Stable. -Neutron to proton ratio can tell stability. Atomic # 1-20 then n:p=1.00. Atomic # 21-40 n:p=1.25. Atomic # 41-83 n:p=1.50. If these are not equal, nucleus is likely unstable. Ratio larger than what’s wanted has too many neutrons and beta emission will occur. Ratio below what’s wanted has too many protons and electron capture or positron willoccur. If >84 there are no stable nuclei, all are radioactive and alpha particles will emit. -A nuclide will generally be stable if the mass # is close to the atomic mass of the element. IV. Nuclear Transmutation- A non-spontaneous process where a nucleus collides with a nuclear particle or another nucleus. Ernest Rutherford was the first to do this. -Particle Accelerators- atom smashers- strong magnetic and electrostatic fields that move charged particles. -Shorthand transmutation: 147N (42He,11H)178OABOVE: nitrogen is target reactant, He is what bombards N producing H and O. V. Radioactive Decay- Rate is always first order. -Half-life- Time required for ½ of the nuclei in the sample to decay. NOT affected by temp, pressure or chemical
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