CHEM 2060 Midterm: Lecture notes before Midterm 1

• School: University of Guelph
• Department: Chemistry
• Course: CHEM 2060
• Professor: Jason Thomas

Document Summary

A crystal identical particles (atoms, ions, or molecules) arranged periodically in a regular, repeating pattern, imagined as a lattice. Diffraction s(cid:272)atteri(cid:374)g a(cid:374)d (cid:271)e(cid:374)di(cid:374)g of (cid:449)a(cid:448)e arou(cid:374)d o(cid:271)je(cid:272)ts (cid:449)he(cid:374) the (cid:449)a(cid:448)e(cid:859)s (cid:449)a(cid:448)ele(cid:374)gth a(cid:374)d the objects dimensions are comparable in size. X-rays light with wavelengths comparable to molecular dimensions. Crystallography theory and analysis of periodically organized crystals within a perfectly ordered lattice over a long-range (long compared the the probing wavelength involved). Atoms and molecules in a crystal are well suited to this. The technique requires that crystalline samples of the analyte (species being analyzed) be used. X-rays pass through crystal and interact with electrons (not the atomic nuclei: does(cid:374)(cid:859)t (cid:373)easure the (cid:374)u(cid:272)lei, it (cid:373)easures the ele(cid:272)tro(cid:374)s arou(cid:374)d it. Regions of high electron density interact more strongly. (h atoms not usually observed in xrd because electron density is so low) Use a mathematical algorithm to create model of molecular arrangement from the pattern. Bonds deduced from relative distance between nuclei.