<p>All known molecules belong to one of 32 Symmetry Groups (Point Groups).</p><p>Assigning the Point Group of a molecule.</p><p>Follow the questions in the Flow Chart to find the Point Group label of the molecule.</p><p>The ‘Special Groups’ – Linear (C∞v, D∞h) Tetrahedral (Td), Octahedral (Oh) and Icosahedral (Ih)– are eliminated first.</p><p>Then the distinction between Rotation(C, D, S) and non-Rotation groups (Ci, Cs, C1).</p><p>Then the distinction between simple rotation (C), dihedral rotation (D) and improper rotation (S) groups.</p><p>There are tables in nearly all Inorganic, Physical and Spectroscopy textbooks that give all the symmetry operations (elements) of the Point Groups.</p><p>From CM3003 exam 2005</p><p>Summer (i) List, and then illustrate, the elements of symmetry in each of the following species. State to which point groups these molecules belong?</p><p> a) O=PCl3</p><p> b) tetrachloroethene, C2Cl4</p><p> c) IF5</p><p>2- e) [PtCl4] (8 marks) Autumn (i) List, and then illustrate, the elements of symmetry in each of the following species. State to which point groups these molecules belong?</p><p> a) SF4 b) 1, 4 - dichlorobenzene</p><p> c) IF5</p><p>- d) the cyclopentadienyl anion [C5H5] (8 marks) The elements of a Group are collected into Classes. A Class is a set of symmetry operations that are identical except for their orientation. </p><p>(The real definition is much more detailed.)</p><p>C2v : E C2 σv(yz) σv(xz) (4 Classes)</p><p>C3v : E 2C3 3σv (3 Classes)</p><p>D2h: E C2(z) C2 (y) C2 (x) i σv(xy) σv(xz) σv(yz) (8 Classes)</p><p>2 3 D5d: E 2C5 2C5 5C2 i 2S10 2S10 5σd (8 Classes)</p><p>Td: E 8C3 3C2 6S4 6 σd (5 Classes)</p><p>φ 2φ 3φ C∞v: E 2C∞ 2C∞ 2C∞ … ∞σv (∞ Classes)</p>