A Pedagogical Illustration of the Determination of the Nature and Strength of Bonds in Crystalline Compounds from X-ray Diffraction and Infrared Spectroscopy Studies

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 6 Issue 2 (2001) pp 73-77

A Pedagogical Illustration of the Determination of the Nature and Strength of Bonds in Crystalline Compounds from X-ray Diffraction and Infrared Spectroscopy Studies

Pierre Couchot,^† Sandrine Monney,^*,† George D. Sturgeon,^‡ and Michael Knorr^†

^†Département de Chimie, Université de Franche Comté, 25030 Besançon Cedex, France, ^‡Department of Chemistry University of Nebraska, Lincoln, Nebraska 68588
Received June 29, 2000. Accepted October 17, 2000

Published online: 9 March 2001

Abstract. This article describes a method used to teach students how X-ray crystallography and infrared spectroscopy analysis can be used to obtain information about the nature and strength of the bonding in the crystalline compounds M^IM^III(SO₄)₂ (with M^I = K⁺, Rb⁺, Cs⁺ and M^III = Al³⁺, Cr³⁺, Fe³⁺). These sulfates form an isomorphic series. The influences of specific M^I and M^III ions on the variation of the a and c parameters and on the position of IR absorption bands are described. Additionally, X-ray crystallography and infrared spectroscopy studies of the double sulfates M^IM^III(SO₄)₂ show students the existence of [SO₄–M^III–SO₄]– layers in the crystallized products; the covalent character of M^III–O attractions, which give cohesion in these layers; the existence of M^I layers between [SO₄–M^III–SO₄]– layers, and the electrovalent character of M^I–O interactions.

Key Words: In the Classroom; physical chemistry; X-ray; crystallography; crystals

(*) Corresponding author. (E-mail: sandrine.monney@univ-fcomte.fr)

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