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Chemistry Unit 3 Chemical Bonds

Chemistry Unit 3 Chemical Bonds. V alence Electrons Dot Diagrams Oxidation numbers Types of Bonds Polyatomics Transition elements. Valence Electrons. The number of electrons in the outer energy level involved in bonding. Equal to the ‘group number’ (except 3-12).

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Chemistry Unit 3 Chemical Bonds

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  1. Chemistry Unit 3Chemical Bonds Valence Electrons Dot Diagrams Oxidation numbers Types of Bonds Polyatomics Transition elements

  2. Valence Electrons • The number of electrons in the outer energy level involved in bonding. • Equal to the ‘group number’ (except 3-12). • Found in loop and cross diagrams.

  3. Dot Diagrams • Used to show the valence electrons with the symbol. . . . . . N H And . .

  4. WB Practice! • Aluminum • Boron • Sulfur • Calcium

  5. Oxidation Numbers The number of electrons that an element would like to gain or lose to complete its outer valence shell. All atoms and compounds want to have a complete outer shell. 8 electrons (An Octet) completes any outer shell. They come from the valance electrons.

  6. Oxidation Numbers • From valence electrons: • Valence 1-3 want to lose. • Valence 5-7 want to gain. • Valence of 4 can go either way. So… H, Li, and Na have oxidation numbers of 1+ because they would like to give one electron away to be ‘stable’. While… F, Cl and Br has oxidation numbers of 1- because they would like to get one electron to be ‘stable’.

  7. Types of Bonds • Ionic: • Where electrons are lost and gained between atoms. • Mainly between metals and non-metals. • Uses the Oxidation number • Covalent: • Where electrons are shared between atoms. • Between two non-metals. • You must be given the number of each element used. • For BONDING: • Elements to RIGHT of the stair step are NON-metal • Elements to the LEFT of the stair step are METAL

  8. Examples of Ionic Compounds • Sodium and Chlorine: (Na 1+ and Cl1-) • is NaCl • Potassium and Bromine: (K 1+ and Br 1-) • is KBr • Magnesium and Oxygen: (Mg 2+ and O 2-) • is MgO • Calcium and Sulfur: (Ca 2+ and S 2-) • is CaS

  9. Ionic Bonds Demo 1+ 2- H O • Hydrogen and Oxygen: • So it takes 2 Hydrogen to bond with one oxygen. • Calcium and Chlorine: • So it takes 2 Cl to bond with 1 Ca) 1 2 H2O 2+ 1- Ca Cl 2 1 CaCl2

  10. Ionic Bonds - NOTICE • In the final answer – if the subscripts would match, we leave them off. • The positive oxidation always comes first. • Pay very close attention to capital and lower case and the placement of the subscript.

  11. Ionic Bond Practice • Combine: • Potassium and Sulfur • Magnesium and Nitrogen • Calcium and Phosphorous • Aluminum and Chlorine

  12. Examples of Covalent • 1 Carbon and 1 Oxygen is • CO • 1 Carbon and 2 Oxygen is • CO2 • 1 Phosphorous and 3 Chlorine is • PCl3

  13. Covalent Bond Practice • Combine: • 1 Silicon and 4 Fluorine • 2 Nitrogen and 3 Sulfur • 1 Hydrogen and 1 Bromine • 2 Bromine

  14. Polyatomics • Covalent compounds that are “pre-formed” with unique names and charges (oxidations). • They can and will ionically bond with other compounds and elements.

  15. Poly Oxidation 1- (FS) Name Formula C2H3O2 HCO3 ClO3 OH NO3 NO2 CN • Acetate • Bicarbonate • Chlorate • Hydroxide • Nitrate • Nitrite • Cyanide

  16. Poly OXIDATION 2- (FS) Name Formula CO3 CrO4 O2 SO4 SO3 SiO3 • Carbonate • Chromate • Peroxide • Sulfate • Sulfite • Silicate

  17. Poly – Other Oxidations (FS) Oxidation - Name Formula PO4 NH4 NH3 H3O CH4 • 3- Phosphate • 1+ Ammonium • 1+ Ammonia • 1+ Hydronium • 0 Methane

  18. Polyatomic Ionic Examples • Combine: • Aluminum (Al 3+) and Sulfate (SO42-) • Al2(SO4)3 • Potassium (K 1+) and Nitrate (NO31-) • KNO3 • Ammonium (NH41+) and Chlorine (Cl1-) • NH4Cl • Ammonium (NH41+) and Nitrate (NO31-) • NH4NO3

  19. Polyatomic Practice • Combine: • Barium and Hydroxide • Calcium and Sulfate • Ammonium and Hydroxide • Lithium and Nitrate

  20. Transition Elements • The transition elements get their name because they have variable oxidation numbers. • Their oxidation numbers are always positive. • You are told or given a transition elements oxidation number with a roman numeral. • They will bond Ionically with other elements and compounds.

  21. Transition Ionic Examples • Combine: • Copper (I) and Oxygen • (Cu2O) since Cu 1+ and O 2- • Iron (III) and Chlorine • (FeCl3) since Fe 3+ and Cl1-

  22. Transition Ionic Practice Combine: • Lead (II) and Carbonate • Gold (III) and Sulfur • Nickel (II) and Nitrate • Tin (II) and Fluorine

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