AS and A2 Chemistry notes and resources (WJEC specification) - UNIT CH2. Properties, Structure and Bonding
The uses to which materials can be put depend on their properties, which in turn depend on the bonding and structure within the material. By understanding the relationship between these factors, chemists are able to design new materials. The types of forces that can exist between particles are studied, along with several types of solid structures, in order to illustrate how these factors influence properties. The building blocks of materials are the elements and the relationship of their properties to their position in the Periodic Table is illustrated by a study of the elements of the s-block and Group 7. An introduction to organic chemistry provides the basis for an understanding of how the properties of carbon compounds can be modified by the introduction of functional groups.
4.1 - Chemical Bonding
Candidates should be able to:
(a) describe ionic and covalent bonding (including coordinate bonding) and represent this in terms of appropriate 'dot and cross' diagrams;
(b) describe qualitatively the nature of the attractive and repulsive forces between ions in an ionic crystal;
(c) show an understanding of the covalent bond in terms of the sharing (and spin pairing) of electrons and show awareness of the forces of attraction and repulsion within the molecule;
(d) understand the concepts of electronegativity and of bond polarity, recall that bond polarity is largely determined by differences in electronegativity and use given values to predict such polarities;
(e) appreciate that many bonds are intermediate in character between purely ionic and purely covalent and understand the way in which the electron density distribution varies with the ionic character of the bond.
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