Properties and Bonding in Solids

Types of solids:

1) Molecular

2)  Covalent network

3) Ionic

4) Metallic

Molecular

• Formed from van derWaals forces between molecules

• Polar (dipole-dipole and H-bonding)

• Non-polar (London forces)

• Usually soft with low melting points and poor conductivity.

• Forces between particles:  

  -London Dispersion

  -Dipole-Dipole (if molecules are polar)

  -Hydrogen Bonds (if O-H, N-H, F-H)

Fairly soft, moderately low melting point (usually <200), and Poor thermal and electrical conductivity

Covalent network

• Formed from covalently bonded atoms

• Very hard with very high melting points and poor conductivity.

• There are some compounds that do not have molecules, but instead are long chains of covalent bonds (E.g. diamond)

Ionic

• Hard, brittle, high melting points, and poor conductivity.

• Formed an electrostatic attraction of ions

• Form of particles:  Positive and negative ions

• Forces between particles:  Electrostatic attractions

• Properties:  Hard and Brittle

                    High melting point

                     Poor thermal and electrical conductivity in solids

                     Form electrolytes in water and conduct electricity

• Examples:  All typical salts.  e.g. NaCl, Ca(NO₃)₃, MgBr₂

Metallic

• Formed from metal atoms -positive nuclei in electron sea

• Soft or hard, high melting points, good conductivity, malleable  and ductile

• Form of particles:  Atoms

• Forces between particles: (due to delocalized valence electrons)

• Examples:  All metals.  e.g. Cu, Fe, Sn, Au, Ag