1. The Structure and Properties of Solids

2. Ionic Crystals
This ionic bond forms from the interaction of metal (sodium) and non-metal (chloride) ions.
The ions arrange in a crystal lattice structure with alternating packing of the positive and negative ions.
Physical Properties
Hard, brittle solid
When dissolves in water, the solution conducts electricity
High melting points as a result of the strong electrostatic forces
Ex. NaCl, MgO

3. Metallic Crystals
In the solid state metals form a metallic crystal, which is a structure composed of closely packed atoms held together by electrostatic interactions and free- moving electrons.
Electron sea theory  a theory that states that the electrons in a metallic crystal move freely around the positively charged nuclei

4. Metallic Crystals
Unlike ionic crystals, all metallic crystals do not have similar properties.
Ex. Gold is soft and easily moulded while aluminum is harder.
Physical Properties
Shiny or silvery
Melting points can vary, but most have fairly high
Most are fairly strong
Malleable

5. Molecular Crystals
Some substances form crystal lattice structures when in the solid state.
Molecular crystals are similar to ionic crystal lattices except that they are often more complex.
Ex. Water can form several different types of structures in the frozen form. Example No two snowflakes will every look alike.

6. Molecular Crystals
The intermolecular forces within a molecular crystal determine its structure and properties.
Polar molecules -> have dipole-dipole forces <-very strong force
Non-Polar  have London dispersion forces <-very weak force
Physical Properties
Do not conduct electricity
Have lower melting points
Less hard than ionic crystals

7. Covalent Network Crystals
Is a solid in which the covalent bonds between atoms from an interwoven network.
Diamond
The hardest naturally occurring substance on earth
The carbon atoms in a diamond molecule form a tetrahedral shape
Physical Properties
Very high melting points
Extreme hardness
The covalent network is very strong.
The strength comes from the interlocking network structure.
Poor conductors of electricity.

8. Covalent Network Crystals
Carbon atoms can form other structures in addition to the structure found in diamond. Carbon atoms can form layers or sheets when in the solid phase or large spherical molecules.

9. Homework