Types of Structures

Types of Structures

In a gas or liquid, atoms or molecules can move around randomly. In a solid, the atoms are fixed in positions. They can at most vibrate on the spot. (Vibrate as in move to and fro, not as in expanding and contracting rapidly.)

There are generally two ways in which atoms in a solid are arranged. Atoms in a salt or metal normally arrange themselves in a regular way. This means that we can always find a few atoms whose pattern repeats itself over and over until it fills the whole volume, and nowhere would it look different. Atoms in glass or soot are arranged quite randomly, with no repeating pattern.

Solids in which atoms are arranged in repeating patterns are said to crystalline. Solids in which atoms are arranged randomly are said to be non-crystalline, or amorphous.

We cannot see atoms with our eyes. How can we tell if a solid is crystalline or not? We can find out using an experiment called X-ray diffraction. We may talk about this later on.

The Physics Notes