1. 3.11.3 IMF and Solids Image:Wikimedia Commons User Alchemistry-hp

2. Which is stronger (has a higher melting point) Solids are strongest …so must be held together by stronger forces Liquids are weaker Gases are weakest… lowest melting point… So what is the strongest solid on Earth????

3. Did you say diamonds??? The carbon atoms in diamonds are held together and make a … 1.Covalent network solids – where atoms are covalently bonded to each other. Example: diamond C (diamond)

4. CC Covalent network solids C There are some compounds that do not have molecules, but instead are long chains of covalent bonds (Ex. diamond) CCCCCCCCCCCCCC This happens in 3 dimensions, creating a crystal Because there are only covalent bonds, network solids are extraordinarily strong

5. Covalent network solids 1.Strongest solids 2. Harder solids 3.Higher melting points a)To melt such a solid, covalent bonds must be broken 4.Insoluble in all common solvents a)For solution to occur, covalent bonds must be broken 5.Poor electrical conductors Three dimensional structure based on tetrahedrally bonded carbon atoms. Other Covalent network solids: Silicon Si Quartz SiO 2 Graphite C (s ) – this is a different form of solid carbon

6. A network solid or covalent network solid is a chemical compound in which the atoms are bonded by covalent bonds in a continuous network. In a network solid there are no individual molecules and the entire crystal may be considered a macromolecule. Examples of network solids include diamond with a continuous network of carbon atoms and silicon dioxide also known as quartz with a continuous three- dimensional network of SiO 2 units. Graphite have continuous two-dimensional layers covalently bonded within the layer with other bond types holding the layers together

7. 2. Ionic crystals Ionic compounds (between metal and nonmetal) form crystal lattices Ions are locked into this crystal lattice. It makes them highly ordered and rigid This makes them very Strong

8. High melting points Hard, but brittle Conduct electricity in the liquid phase and in solution Do not conduct in solid phase – Ions must move in order for the material to conduct electricity. - Ions can only move if the substance is melted or dissolved in water Many dissolve in water (polar), but not in covalent solvent (like CCl 4 ) Ionic crystals cont’d

9. + + + + + + + + + – – – – – – – – – – – – – – – – – – 3. Metallic crystals Solid metals consist of regular arrays of metal atoms forming a crystal lattice Metals normally occur as solids (high melting points). Thus, there must be strong bonds between the atoms of metals causing them to bond Bonding in metals and alloys is different from in other compounds: positive nuclei exist in a sea of electrons (this explains why metals conduct electricity)

10. Metallic Solid metals consist of regular arrays of metal atoms forming a crystal lattice Delocalized valence electrons form a “sea of electrons” that can move freely throughout the metal Delocalization provides stability The “electron sea” is also present in the liquid phase Pyrite antimony Bismuth copper

11. 4. Molecular solids Strong covalent forces within molecules But IMF weak Solids are soft with low melting points Sulfur, S 8 Phosphorus, P 4

12. 5. Amorphous solids: 5. Amorphous solids: considerable disorder in their structures (glass, plastic).