Scientific American Magazine

Materials are solids, and solids are divided into two general categories: crystalline, in which the atoms are stacked in more or less regular arrays, and amorphous, in which they are not

The gas of electrons that binds metal atoms together makes metals behave as they do. Their mechanical properties in particular flow from the close-packed crystal structure favored by the metallic bond

They usually consist of metallic and nonmetallic atoms joined by bonds that are partly ionic and partly covalent. This gives them properties such as hardness, brittleness and resistance to heat

The geometry of glass structure is the geometry of disorder on the way to order. The art of the glassmaker can be explained in terms of thermodynamics, chemical bonding and molecular architecture

In synthesizing long-chain molecules man imitates natural polymers such as cellulose. Today nature is being outdone, and polymers are evolving that may be rigid enough to serve for heavy construction

Metals, ceramics, glasses and polymers can be combined in materials that have unique properties of their own. Nature uses this principle in wood and bone; man applies it in a new family of supermaterials

How is heat conducted through a material? The key is the phonon, a particle-like packet of waves that can travel through a solid although the atoms in the crystal lattice are anchored in place

Materials differ In their resistivity to an electric current by as much as 23 orders of magnitude. The insights of quantum mechanics are helping to make this full range more accessible to technology

In dealing with solid materials the chemist is concerned not only with such matters as corrosion and chemical syntheses but also with chemical events that occur inside solids, for example precipitation

Why atoms are magnetic is well understood, but why some materials are magnetic is less so. Nonetheless, advances in magnetic materials have made possible devices from refrigerator latches to computer memories

The quantum-mechanical interpretation of the spectroscopic characteristics of the elements has made possible a number of technological advances such as the development of lasers

Now that the properties of all materials are better understood, it is clear that quite different materials can be used for the same purpose. This calls for subtle choices involving both technology and economics