Type of Solid Particles Attractive Force Properties Examples. ionic positive ions electrostatic solid poor conductor NaCl KNO 3

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1 Soids&Materials 1 Solids & Materials Summary of Properties and Types of Solids Type of Solid Particles Attractive Force Properties Examples ionic positive ions electrostatic solid poor conductor NaCl KNO 3 and negative ions liquid good conductor high melting point molecular molecules wan der Walls poor conductor H 2 O N 2 HCl or dipole low melting point C 12 H 22 O 11 network atoms covalent bonds poor conductor C SiO 2 very high melting point metallic positive ions metallic bond good conductor Ag Cu Fe Hg and free electrons high melting point (not rigidly bonded so can change shape of solid without breaking) Type of Solid Melting Point ( o C) examples: ionic NaCl 801, FeO 1370 molecular Cl 2-100, H 2 O 0, benzene C 6 H 6 5.5, C 18 H covalent or network SiO , C diamond >3550 (C highest mp element) metallic Cu 1083, Fe 1535

2 Soids&Materials 2 Some definitions amorphous no well developed crystal structure (glass has amorphous structure) isomorphous same crystal structure polymorphous same substance but different crystalline structure (allotropes) examples with P and C below Structure of Solids Ionic Compounds Structure and Properties determined by: a) Charges on ions b) Relative size of ions c) Polarization of ions Sizes Radius ratio = r+/r- Determines packing r+/r- Type Coordination Number.15 Linear Trigonal planar Tetrahedral Octahedral 6.73 > Cubic 8 Larger positive ion more negative ions can be in contact with Ability of charge cloud to be distorted is polarizability Negative ions are more easily polarized Small positive ions cause distortion of negative clouds Examples of Ionic Crystal Structure 1:1 ratio positive and negative ions but different structure Compound Coordinate Number Structure ZnS 4 Tetrahedral NaCl 6 Octahedral CsCl 8 Cubic

3 Soids&Materials 3 Crystal Structure of Metals Coordinate Number % of Empty Space Position Body centered cubic 8 32% Cubic closest 12 26% a-b-c-a-b-c packed (face centered) Hexagonal closest packed 12 26% a-b-a-b Most metals are distributed among these three types Density of many metals is high

4 Soids&Materials 4 Examples of Allotropes of Phosphorous (polymorphous since P but different structrues) P red, white, black forms White P (P 4 molecules most reactive) It glows greenish in the dark (when exposed to oxygen), is highly flammable and pyrophoric (self-igniting) upon contact with oxygen in air. Red P (chains, intermediate reactivity) Black Phosphorous (layers, least reactive)

5 Soids&Materials 5 Forms of pure Carbon (allotropes of carbon) Diamond is tetrahedral 3 dimensional sp 3 carbons with bonds in all directions Graphite is hexagonal (close packed) chemically bonded layers of sp 2 carbons with only weak vander Waals forces holding layers together. Graphite is made of hundreds of layers of graphene Buckyball such as C 60 C 60 is a molecule of carbon atoms with exactly same shape as a minature soccer ball of hexagons and pentagons Carbon Nanotube tubes of rolled up graphite that can be stronger than steel and some forms are exactly conductors - even better conducting than copper). May be used in future for construction or electronic devices. Graphene is a single layer of hexagonal (close packed) chemically bonded layers of sp 2 carbons. Like atomic chicken wire. It is a better conductor of heat and electricity than copper. It is stronger than steel on a mass basis. It transparent and may be used for touch screen displays in future.

6 Soids&Materials 6 ( Buckyball C60 large.gif&imgrefurl= sites.htm&h=617&w=587&sz=74&hl=en&start=2&tbnid=kzlkxbid3e-- MM:&tbnh=136&tbnw=129&prev=/images%3Fq%3Dbuckyball%2B%2BC60%26gbv%3D2%26svnum%3D10%2 6hl%3Den%26sa%3DG Carbon Nanotube 3Den%26sa%3DG

7 Soids&Materials Graphene 7