Structure and Properties of Solids 4.8

Structure of Solids Crystalline: atoms, ions, or molecules are well ordered. Have a well-defined melting point. Often the solid has regular shapes. Amorphous: no order to the particles. Examples are glass and rubber. Have no defined mp; they soften over a range of temperatures (important for glass blowing)

Unit cell: crystal lattice In a brick wall there is a repeating pattern, as there is with most wallpaper In a crystalline solid there is a repeating pattern - the unit cell. The unit cell repeats to make the crystal lattice

The seven unit cells

Three Cubic lattices

Close Packing

Another way of looking at it

Diamonds are a …..

Some ionic solids- lattice decided by size & charge

From sea to shining ... array of metal ions in a sea of electrons A sea of valence electrons Electrons not tightly held but can move Explains electrical conduction Also explains optical properties - most metals “shine”