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

─

+

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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