TABLE OF CONTENTS The term metal is familiar to everyone, but many people would have difficulty defining it other than by specifying that a given material possesses some metallic characteristics. More accurately, a metal is a chemical element that is lustrous, hard, malleable, ductile, and usually a good conductor of heat and electricity. Of all the elements, 73 are classified as metals. More sophisticated definitions of metals are available but are beyond the scope of this book.
The atoms in a metal are arranged in a definite order and pattern, which repeat itself in all three directions. This is typical for all crystalline materials. The orderly arrangement of the atoms in the crystal is also referred to as the space lattice. The distance between the atoms is measured in angstroms and depends on the individual material and its temperature; an angstrom (1 ) is a unit of length equal to 1 10 -10 m or 4 10 -9 in. Most metals in everyday life consist of many crystals and are called polycrystalline. Only under special conditions can a single crystal of metal be obtained. The polycrystalline structure is the result of how metals solidify from the molten liquid. As the liquid is cooled, many nuclei of crystals form and start growing simultaneously. As these solid nuclei grow, they consume the liquid metal until the walls of the expanding crystals (in all...
