In this module, we will present basic concepts of atomic and molecular structure that lay a foundation for the discussion throughout the book on the nature, properties, and uses of materials. The ability to grasp these fundamental materials technology concepts not only allows you to deal with today's materials and processes, but also prepares you for new developments in materials. The structure of materials follows the structure of a building because both develop through the joining of smaller units. Particles of earth form bricks, bricks are stacked together to form walls, walls form rooms, and rooms make a building. Matter is anything that has mass and occupies volume.
Plasma exists only under drastic conditions.
At very high temperatures, matter is shredded into positively charged particles. These charged particles move about in a cloud of negatively charged electrons. When two or more atoms are joined by covalent bonds, the unit of matter formed is called a molecule. An element is a sub-stance that cannot be broken down any further by chemical reaction. Examples of elements are carbon, oxygen, or sulfur.