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.

6.2 - Trends in properties of the elements of the s-block and Group 7 (17)

Candidates should be able to:

(a) recall the typical behaviour of the elements of Groups 1 and 2 with O2, H2O and Group 2 elements with dilute acids (excluding nitric acid) and the trends in their general reactivity ¢Ó;

(b) describe the reactions of the aqueous cations, Mg2+, Ca2+ and Ba2+ with . OH , CO3 2. and SO4 2. ¢Ó;

(c) recall the formulae of the oxides and hydroxides of Groups 1 and 2 and appreciate their basic character;

(d) recall the flame colours shown by compounds of Li, Na, K, Ca, Sr and Ba (and that Mg compounds show no colour) and describe their use in qualitative analysis;

(e) show an awareness of the importance of calcium carbonate and phosphate minerals as skeletons for living systems and the consequent formation of carbonate rocks and the importance of calcium and magnesium in biochemistry;

(f) recall the trend in volatility shown by the elements Cl, Br and I and relate to chemical bonding;

(g) recall and explain the tendency of the halogens (F . I) to react by forming anions ) I Br Cl F ( . . . . , , , , and recollect that this reactivity decreases on descent of the group *;

(h) recall the reactions of the halogens with metals, their displacement reactions with halides, and explain the group trends and displacements in terms of the relative oxidising power ¢Ó*;

(i) understand the displacement reactions of Cl2 and Br2 in terms of redox ¢Ó*;

(j) recall the nature of the reaction between aqueous Ag+ and halide ) I Br Cl ( . . . , , ions* followed by dilute aqueous NH3 , and understand the analytical importance of these reactions in qualitative analysis (ionic equations required for precipitation reactions only).