ABSTRACT
From the previous chapters we have gained an understanding as to the structure and bonding of atoms. We now need to consider larger structures that consist of an aggregate of many atoms. For engineering purposes materials can be classified as crystalline (atoms or molecules containing long-range order) or amorphous (atoms or molecules without long-range order). The formula for common salt is NaCl, which tells us the ratio of atom species present in the material and as a solid the repeating atomic unit, which makes up a crystal of salt. If the salt is dissolved in water it dissociates to its ionic species Na
and Cl
and the container defines the shape of the liquid.