Chemical Bonds   The Formation of Ions   Atoms tend to lose or gain electrons that results in the outermost shell being filled to capacity 10/12/2015APHY1011

Chemical Bonds   The Formation of Ions   Why does Cl attract another electron if its neutral? 10/12/2015APHY1012 Position Probability

Chemical Bonds   Covalent Bonds   Atoms held together by their mutual attraction for shared electrons 10/12/2015APHY1013 Non-polar molecule Polar molecule ─ +

Chemical Bonds   Metallic Bonds   The positive metal ions are held together by a “fluid” of free electrons removed from the outer shells of the metal atoms 10/12/2015APHY1014

Chemical Bonds 10/12/2015APHY1015

Chemical Bonds   Bonds between molecules, not within molecules Usually involves dipoles with PE ~ 1/r 6Usually involves dipoles with PE ~ 1/r 6 Important in liquids and solidsImportant in liquids and solids   DNA has weak H bonds between each strand of the molecule Broken by molecular collisionBroken by molecular collision Important in protein synthesisImportant in protein synthesis 10/12/2015APHY1016

Chemical Bonds 10/12/2015APHY1017

Chemical Bonds   Natural Sources to Pure Metals   Ores – materials containing high percentage of a mineral that make extraction feasible. Concentrated by floatation after grinding into a powder.   Refining removes the impurities by heating (slag formation) or chemical reactions (electrolysis) 10/12/2015APHY1018

Chemical Bonds   Natural Sources to Pure Metals   Alloys – mixtures of metals or with a nonmetal that have properties more desirable than the pure metal. Cu + Au → increased hardness of gold Ni + Cr + Fe → iron is less likely to rust 10/12/2015APHY1019

Chemical Bonds   Natural Sources to Pure Metals   Cast iron – brittle when cold Engines, boilers, stoves, cookware, pipes   Wrought iron – hardened iron by hammering out remaining impurities. Fences, gates, grills 10/12/2015APHY10110

Chemical Bonds   Natural Sources to Pure Metals   Carbon steel: < 1.5% C + Fe Beams, girders, rebar, cutting tools, railroad rails   Stainless steel:Ni + Cr + Fe Cutlery, chemical plants, ornaments for buildings   Silicon steel: Si + Fe Transformers, motors, generators 10/12/2015APHY10111

Chemical Bonds   Polymers   Large molecules made of carbon chains   Synthetics – rayon, cellophane, plastics, rubber, polyester, Velcro, medical (hip, skin, artery) 10/12/2015APHY10112

Chemical Bonds   Composites   Heterogeneous mixture that exploits the desired structural and mechanical properties of each material Fiber-reinforced polymers: fiberglass with resin Light weight and strong – automobile bodies, fishing rods, bicycle frames, bathtubs Kevlar 10/12/2015APHY10113