2. Properties of Solids  Definite shape and volume  Particles are close together so attractive forces (bonds and IMFs!) are strong  Highly ordered  Rigid, incompressible

3. Two categories of solids  Crystalline Solids: have a regular structure in which particles pack in a repeating pattern from one edge of the solid to the other  Amorphous Solids: “solids without form” Have little structure. Includes glass and many plastics

4. Crystalline Solids  4 types of crystalline solids based on the types of attractive forces that hold them together. 1. Molecular solids 2. Covalent network solids 3. Ionic solids 4. Metallic solids

5. Molecular solids  Composed of molecules held together by IMFs  Relatively soft with low melting and boiling points  Water, sugar, ammonia are all examples

6. Covalent solids  Form crystals that can be viewed as a “giant” molecule that is held together by an endless number of covalent bonds  Hard, higher melting points and boiling points  Diamond, graphite, quartz are examples

7. Graphite and diamond

8. Ionic solids  Held together by the strong force of attraction between oppositely charged ions (cations and anions)  Hard, brittle, high melting and boiling points  Will conduct electricity when in aqueous solutions but not as solids  Salts are examples

9. Ionic solids  Exist as a 3D repeating pattern called a crystal lattice  Many ionic solids will dissolve in water and dissociate into ions to exist at a lower energy

10. Ionic Bond Strength  A measure of the attractive forces between the ions  Smaller ions=stronger ionic bonds  Fewer atom ratio=stronger ionic bonds  Evidence comes from melting points!  KCl has a higher melting point than KI because Cl is smaller than I  FeCl 2 has a higher melting point than FeCl 3 because there are fewer atoms

11. Metallic Solids  Malleable and ductile  Held together by “metallic bonds”  Have their valence electrons delocalized over many atoms  Good conductors (mobile particles)  “electron sea” like fruit in jello  Examples are gold, aluminum, iron

13. Why are metal solids malleable while ionic solids are brittle?

14. Types of crystalline solids TypeAttractive Force Example MolecularIMFsDry ice, sugar, water Covalent Network Covalent bond Diamond, graphite IonicIonic bondsNaCl, ZnS MetallicMetallic bonds Au, Cu, Ag

15. Amorphous Solids  No regular geometric pattern  Jumbled up: typically long chains of molecules that get tangled up  Held together by IMFs  Ex: waxes