[Jose M.]

Hi. Happy new year 2006.

I have a question about solids...crystaline solids. I know there are also amorphous (disordered) solids, but I ask about crystaline (ordered) solids. Which are the seven (7) types of crystaline solids ? I shall discuss the four (4) that I know.

1) Covalent crystals. Particles joined by covalent bonds. Examples: diamond and graphite, both forms of elemental (inorganic) carbon.

2) Ionic crystals. Particles are ions, joined by ionic bonds. Examples: salts, such as NaCl, KCl and NaF.

3) Molecular crystals. Particles are molecules, joined by intermolecular forces. Examples: sucrose (table sugar) crystals (rock candy) (sucrose is a disacaride made of one glucose & one fructose). Another example is ice (frozen water).

4) Metallic crystals. Particles are metal atoms (atoms with three or less valence electrons) , joined by metallic bond ("sea" of electrons). Examples: silver, gold & platinum.

Those are the four (4) types of crystaline solids that I know. Which are the other three (3) ?

[AWK]

Therer are 7 crystallographic systems - triclinic, monoclinic and so on.