CHEM 251 1st Edition Lecture 9 Outline of Last Lecture I. Clicker QuestionsII. Group ProblemsOutline of Current Lecture III. Clicker QuestionIV. Intro to SymmetryV. Symmetry OperationsCurrent LectureVI. Clicker Questiona. Assign the point group: Answer: C2vIII. Intro to Symmetrya. Symmetry: language used to describe the readily apparent symmetry in molecular geometryb. Symmetry operations: action that leaves the molecule in a form indistinguishablefrom the original c. Symmetry elements: point, line, or plane around which symmetry operations are performedd. Point groups: unique label that describes all symmetry elements of a moleculeIV. Symmetry Operationsa. Identity (E)i. Do nothingb. Proper Rotation (Cn where n=360/degrees of rotation)i. Rotate the moleculec. Reflection (σ)i. Reflect the molecule across a planed. Inversion (i)i. Reflect the molecule through a pointThese 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.e. Improper Rotation (S)i. Rotation about an axis followed by reflection across a planef. Example: BF3i. Found a C3 axis => 3-fold rotation has 3 mirror planesii. Next-look for perpendicular rotational axes1. Three C2 axes2. Axis w/ highest n = z-axis3. Perpendicular axes of rotation => Dn point group 4. There is also a horizontal mirror planeg. Special point groupsh. Use flow
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