Six Types: 1) Dipole - Dipole, 2) Hydrogen-Bonding, 3) London Dispersion, 4) Metallic,

1. Forces holding crystals together • Six Types: 1) Dipole - Dipole, 2) Hydrogen-Bonding, 3) London Dispersion, 4) Metallic, 5) ionic, 6) Covalent (network solids)

2. Types of Crystalline Solids Ionic Solid: contains ions at the points of the lattice that describe the structure of the solid (NaCl). Molecular Solid: discrete covalently bondedmolecules at each of its lattice points (sucrose, ice).

3. Types of Crystalline Solids Atomic Solid: Atoms at the points of the lattice that describe the structure of the solid (only one type of atom – diamond, graphite, copper).

4. Types of Crystalline Solids

5. Types of Crystalline Solids Molecular Solid: discrete covalently bondedmolecules at each of its lattice points (sucrose, ice).

6. Intermolecular forces • Intermolecular forces (IMF) have to do with the attraction between molecules versus the attraction between atoms within a molecule.

7. Molecular Solids • WITHIN MOLECULES, STRONG COVALENT BONDS BETWEEN MOLECULES, RELATIVELY WEAK FORCES (Intermolecular Forces)

8. Intermolecular forces • Two Types: 1) Dipole - Dipole Forces Hydrogen-Bonding 2) London Dispersion (van der Waals) Forces,

9. + – H Cl + – + – + – + – Dipole - Dipole attractions • Polar molecules have a separation of charge • Molecules are attracted to each other in a compound by these + and – forces.

10. Hydrogen - bonding • H-bonding is a special type of dipole - dipole attraction that is very strong • It occurs when N, O, or F are bonded to H • They are given a special name (H-bonding) because compounds containing these bonds are important in biological systems

11. Water Molecules

12. London Dispersion forces • Non-polar molecules do not have permanent dipoles. • London dispersion (or van der Waal) forces exist in non-polar molecules are due to small dipoles that are temporary.

13. London Dispersion forces • Because electrons are moving around in atoms, there will be instants when the charge around an atom is not symmetrical • The resulting tiny dipoles cause attractions between atoms/molecules

14. London Dispersion forces • relatively weakforces that exist among noble gas atoms and nonpolar molecules. (Ar, C8H18)

15. London forces Induced dipole: Instantaneous dipole: Eventually electrons are situated so that tiny dipoles form A dipole forms in one atom or molecule, inducing a dipole in the other

16. METALLIC SOLIDS Atomic Solid: Metal Atoms at the points of the lattice.

17. Metallic BondingThe Electron Sea Model Regular Array of Cations in a “Sea” of Valence Electrons

18. B. Types of Bonds Metals are good conductors because the valence electrons are able to flow freely Valence electrons of metals can be thought of as a “sea of electrons”

19. B. Types of Bonds Metallic Bonding - “Electron Sea”

20. B. Types of Bonds • Metallic Bonding • Metals are found in: • Groups 1 & 2 • middle of table in 3-12 • Below and to left of stairstep line • Have luster, are dutile and malleable

21. B. Types of Bonds METALLIC e- are delocalized among metal atoms, “electron sea” Bond Formation atom Smallest Unit Types of Elements metals

22. IONIC SOLIDS Contains ions at the points of the lattice (NaCl). • HIGH MELTING SUBSTANCES • HELD TOGETHER BY STRONG ELECTROSTATIC FORCES THAT EXIST BETWEEN OPPOSITELY CHARGES IONS

23. NaCl

24. II. Octet Rule • In the formation of compounds, atoms tend to achieve the electron configuration of a noble gas. • Atoms either gain, lose, or share electrons to form compounds.

25. III. Cations Loses an e- -An atom’s loss of valence electrons produces a cation, or a positively charged ion.

26. III. Cations • Metals – lose valence e- easily • Transition metals – have 2 valence e-, usually lose those two to form 2+ ions, but can also lose d electrons to form other ions

27. IV. Anions • Nonmetals easily gain e- to form negative ions to get to 8 valence e- Gains an e- Chloride ion

28. IV. Anions • -Nonmetals usually gain e- • Some can gain or lose, but will gain most often

29. Formula Unit -The lowest whole-number ratio of ions in an ionic compound.

30. V. Ionic Bonds • When oppositely charged ions attract, electrostatic force that holds them together = ionic bond • Compounds containing ionic bonds = ionic compounds • Electrons are transferred from cations to anions • Bonds formed between metals and nonmetals (or contain a polyatomic ion)

31. V. Ionic Bonds Na· 1s2 2s2 2p63s1 1s2 2s2 2p6 3s23p5 RESULTS IN Na+ 1s2 2s2 2p6 1s2 2s2 2p6 3s23p6

32. VI. Properties of Ionic Compounds • Most ionic compounds are crystalline solids at room temperature. • Arranged in repeating three-dimensional patterns • Ionic compounds generally have high melting points • Large attractive forces result in very stable structures

33. VI. Properties of Ionic Compounds • Ionic compounds can conduct an electric current when melted or dissolved in water. • When ionic compounds are dissolved in water the crystalline structure breaks down. This allows the ions to move freely which results in conductivity.

34. The positive Na ions move to the cathode and the negative Cl ions move to the anode.

35. NETWORK ATOMIC SOLIDS: (CARBON & SILICON) SOLIDS CONTAINING STRONG DIRECTIONAL COVALENT BONDS TO FORM A SOLID THAT MIGHT BE BEST VIEWED AS A “GIANT MOLECULE” EXAMPLE: DIAMOND AND GRAPHITE

36. The Structures of Diamond and Graphite

37. The Structure of QuartzSi at the center of tetrahedralarrangement with 4 oxygen atoms.