Post on 13-Jan-2016
Chemical BondsChemical Bonds The Formation of Ions
Atoms tend to lose or gain electrons that results in the outermost shell being filled to capacity
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Chemical BondsChemical Bonds The Formation of Ions
Why does Cl attract another electron if its neutral?
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Position Probabili
ty
Chemical BondsChemical Bonds Covalent Bonds
Atoms held together by their mutual attraction for shared electrons
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Non-polar molecule Polar molecule
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Chemical BondsChemical 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
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Chemical BondsChemical Bonds
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Chemical BondsChemical Bonds Bonds between molecules, not within molecules
• Usually involves dipoles with PE ~ 1/rUsually involves dipoles with PE ~ 1/r66
• 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
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Chemical BondsChemical Bonds
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Chemical BondsChemical 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)
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Chemical BondsChemical 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
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Chemical BondsChemical 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
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Chemical BondsChemical 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
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Chemical BondsChemical Bonds Polymers
Large molecules made of carbon chains
Synthetics – rayon, cellophane, plastics, rubber, polyester, Velcro, medical (hip, skin, artery)
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Chemical BondsChemical 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
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