Introduction to Symmetry Operations and Point Groups

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September 6, 2023

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  • In this short educational video, Rosie Lester introduces us to symmetry operations and symmetry elements and point groups. The focus of the video is on small organic molecules for an easy visualisation. Rosie demonstrates the effects of identity, inversion, rotation, reflection, and improper rotation symmetry operations on representative molecules, for example showing symmetry operations for benzene. Then, we will see how to determine point groups thanks to the symmetry operations identified using a flow chart. You can then test yourself on symmetry operations, elements, and point groups with example molecules. In this video: - 01:18 Brief introduction to symmetry operations and associated symmetry elements (including: 04:18 Symmetry operations for benzene) - 08:07 Flowchart to determine point groups based on the symmetry operations. - 08:23 Challenge yourself! Identify symmetry operations and point groups using the chart. The answers are included in the video. Resources: On our website you can find the transcript of this video as a worksheet as well as the flowchart, which can be used for teaching and reviewing. The document contains links to further resources. You can also find practice exercises on point groups in the module "Learning Point Group symmetry through 3D printed models". https://www.ccdc.cam.ac.uk/Community/educationalresources/teaching-modules/ The molecules used to demonstrate these concepts are available in the Cambridge Structural Database (CSD). In particular, we used CSD Entries: FULLER, BENZEN, AYALOC. You can visualise and download the structures for free from CCDC's Access Structures service: https://www.ccdc.cam.ac.uk/structures/ Water, hydrogen cyanide, CHFBrCl, and ethane were instead manually sketched in Mercury, but you can use ConQuest, the CSD searching software (licenced), or Access Structure (free) and WebCSD (licenced), to find structures containing these molecules. The images and animation frames of these molecules are prepared using Mercury. Mercury visualisation software is available to download for free https://www.ccdc.cam.ac.uk/Community/csdcommunity/FreeMercury/ In Mercury you can also visualise symmetry elements on the crystal structure. More advanced functionality from the CCDC enables you explore molecules and structures in more detail. To find out how to access more advanced functionality with a CSD-Core license see https://www.ccdc.cam.ac.uk/solutions/csd-core/ Follow us on social media: Instagram: @ccdc_cambridge Twitter: @ccdc_cambridge Facebook: Cambridge Crystallographic Data Centre (CCDC)

    Chemistry

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