Solids

1. Solids • Two major types: • Amorphous- those with much disorder in their structure. • Crystalline- have a regular arrangement of components in their structure.

2. Crystalline Solids • Lattice- a three dimensional grid that describes the locations of the pieces in a crystalline solid. • Unit Cell-The smallest repeating unit of the lattice.

4. Simple Cubic Number of atoms per unit cell? 1

5. Body-Centered Cubic Number of atoms per unit cell? 2

6. Face-Centered Cubic Number of atoms per unit cell? 4

7. Body-centered Cubic Face-centered Cubic Simple Cubic

8. Types of Crystalline Solids • Ionic solids have ions at the lattice points. • Molecular solids have molecules. • Polar • Nonpolar • Atomic Solids: • Metallic crystals have positive metal ions. • Group 8A crystals have atoms. • Network solids have covalently-bound atoms.

9. Ionic Solids • Particles are held together by attraction of opposite charges. • Huge melting and boiling points. • Particles are locked in lattice positions, so sample is hard and brittle. • Every electron is accounted for so they are poor conductors-good insulators.

10. Molecular solids • Molecules occupy the corners of the lattices. • Different types of molecules have different intermolecular forces.

11. Nonpolar Molecular Solids • The only forces are _______________ _______________________________ • Strength depends on ________________ _________________________________ • Most are gases at 25ºC.

12. Polar Molecular Solids • Possible IMFs: _____________________ _________________________________ • Dipole-dipole forces are generally stronger than dispersion forces. • Hydrogen bonding is stronger than Dipole-dipole forces. • No matter how strong the intermolecular force, it is always much, much weaker than the forces in bonds.

13. Metallic Solids • Electron sea model – array of metal cations in a “sea” of mobile valence electrons

14. Metallic Solids • Electron sea model accounts for known properties of metals: • Malleable • Ductile • Good conductors of heat and electricity • High melting points • Internal bonding must be both strong and nondirectional

15. Atomic Solids (Nonmetallic) • The only forces are _______________ _______________________________ • Strength depends on ________________ _________________________________

16. Network Covalent Solids • Atoms at points of lattice. • Atoms held together in 3-d network by covalent bonds. • VERY few examples. Memorizethese: C(diamond), SiO2(quartz), SiC

17. Silicon Dioxide • also called silica • quartz, sand

18. Carbon Is Special allotropes There are many types of solid carbon: • Coal – amorphous • Diamond- hardest natural substance on earth, insulates both heat and electricity • Graphite- slippery, conducts electricity • Fullerenes – strong, good conductors of heat and electricity

19. Diamond • each Carbon is sp3 hybridized, connected to four other carbons. • Strong array of s bonds • top on the Mohs hardness scale • very high melting point • nonconducting

20. Graphite is different.

21. Graphite is different. • Each carbon is connected to three other carbons and sp2 hybridized. • Flat sheets of 6 member rings with 120º angles throughout • The p bonds extend above and below each sheet.

22. Graphite is different. • p orbitals overlap forming a huge p bonding network. • Electrons are free to move through out these delocalized orbitals. • The layers slide by each other.

23. Fullerenes • composed entirely of carbon • spherical, elliptical, or hollow tube C60 Buckminster fullerene Carbon nanotubes

24. Types of Crystals Types of Interparticle Attractions