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Chemical Bonds

Chemical Bonds. An electrical attraction between two oppositely charged atoms or groups of atoms. Happens when an atom of a nonmetal takes one or more electrons from an atom of a metal so both atoms end up with eight valence electrons. IONIC BONDING. The Octet Rule.

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Chemical Bonds

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  1. Chemical Bonds

  2. An electrical attraction between two oppositely charged atoms or groups of atoms. Happens when an atom of a nonmetal takes one or more electrons from an atom of a metal so both atoms end up with eight valence electrons IONIC BONDING

  3. The Octet Rule • The octet rule says that atoms can become stable by having eight electrons in their outer energy level, as shown in the noble gas, Neon, (or two electrons in the case of some of the smallest atoms).

  4. Electron Dots For Cations • Metals will have few valence electrons • These will come off Ca

  5. Electron Dots For Cations • Metals will have few valence electrons • These will come off • Forming positive ions Ca2+

  6. Electron Dots For Anions • Nonmetals will have many valence electrons. • They will gain electrons to fill outer shell. P P3-

  7. IONIC COMPOUNDS • metal with nonmetal • + ion - ion • Ca+ionanion

  8. Predicting Oxidation Number or Charge from Periodic Table

  9. Forming Cations metalslose e-form cationsoxidation # • group 1A lose 1 +1 charge 1 + • group 2A lose 2 +2 charge 2 + • group 3A lose 3 +3 charge 3 + • group 4A lose 4 +4 charge 4 +

  10. Forming Anions Non-metalsgain e-form anionsoxidation # • group 7A gain 1 -1 charge 1 - • group 6A gain 2 -2 charge 2 - • group 5A gain 3 -3 charge 3 -

  11. +1 0 +2 +3 +4 -3 -2 -1 1 2 +3 3 +2 4 +1 +2 5 6 7 Oxidation Numbers

  12. IONIC BONDING Neutral atoms come near each other. Electron(s) are transferred from the Metal atom to the Non-metal atom. They stick together because of electrostatic forces, like magnets.

  13. Steps for writing ionic bond formulas 1. Determine the oxidation numbers for the two elements or ions. Ca = +2, Cl = -1

  14. Steps for writing ionic bond formulas 2. Write the chemical symbols in the correct order, with the metal ion first and write the oxidation numbers as superscripts. Ca 2+ Cl -1

  15. Steps for writing ionic bond formulas 3. Crisscross the numbers only—not the charge signs—writing the oxidation number of one element as a subscript for the other. Don’t write number 1 either. Ca 2+Cl1- Ca1Cl2 CaCl2

  16. Steps for writing ionic bond formulas 4. Determine whether the formula is in its simplest form. Reduce the subscripts to the simplest from by dividing by a common denominator. Ca+2 O-2 Ca2 O2 = Ca2O2 CaO

  17. Steps for writing ionic bond formulas 5. Check the formula by calculating the total positive and negative charges and confirming that the total charge on the compound is zero. CaCl 2

  18. Practice these! • magnesium and oxygen • aluminum and bromine • sodium and sulfur • potassium and nitrogen MgO AlBr3 Na2S K3N

  19. More Practice! • potassium bromide • calcium oxide • Silver fluoride KBr CaO AgF

  20. Polyatomic ions • Groups of atoms that stick together as a unit, and have a charge • PO43- phosphate • CO32- carbonate • C2H3O41- acetate • Names often end in –ate or –ite

  21. Steps for writing ionic bond formulas 6. POLYATOMIC IONS ACT JUST LIKE ANY OTHER NEGATIVE ION WHEN BONDING Treat polyatomic ion as single unit—don’t change it in any way!

  22. -2 Na SO +1 Na SO 4 2 4 Steps for writing ionic bond formulas

  23. Steps for writing ionic bond formulas polyatomic ions are enclosed in parenthesis if taken more than once in the formula. A subscript outside the parenthesis multiplies everything inside.

  24. +3 -1 Al NO 3 Al NO ( ) 3 1 Steps for writing ionic bond formulas 3

  25. Practice • potassium hydroxide • zinc (II) carbonate • barium chlorate • aluminum phosphate KOH ZnCO3 Ba(ClO3)2 AlPO4

  26. More Practice • calcium acetate • sodium nitrate • aluminum hydroxide • ammonium phosphate Ca(C2H3O2) 2 NaNO3 Al(OH) 3 (NH4)3 PO4

  27. Naming Ionic Compounds 1. name cation - then anion 2. if anion (nonmetal) is a single element ….. then name ends in “-ide”

  28. Naming Ionic Compounds 3. If metal have more than one possible charge (include roman numeral in parenthesis to give charge)* *All metals except: Ag+1, Zn+2, Cd+2, Al+3

  29. Practice (no transitional metals) • Na2O • Mg(OH)2 • Al(NO3)3 • NH4Cl Sodium oxide Manganese (II) oxide Aluminum nitrate Ammonium chloride

  30. Practice with transitional metals Hint: look at the subscript in the anion to predict the metal oxidation number. • Sn(ClO3)4 • Cu2CO3 • Fe2O3 • NiSO4 Tin(IV) chlorate Copper (I) carbonate Iron (III) oxide Nickel (II) sulfate

  31. Properties of Ionic Compounds • Crystalline structure. • A regular repeating arrangement of ions in the solid. • Ions are strongly bonded. • Structure is rigid. • High melting points- because of strong forces between ions.

  32. Crystalline structure The repeating unit is called the unit cell 3 dimension

  33. Crystalline structure The POSITIVE CATIONS stick to the NEGATIVE ANIONS, like a magnet. + + - - - - + + - + - + + - - - + +

  34. + - + - - + - + + - + - - + - + Ionic solids are brittle

  35. - + - + - + - + + - + - - + - + Ionic solids are brittle • Strong Repulsion breaks crystal apart.

  36. Cubic

  37. Body-Centered Cubic

  38. Face-Centered Cubic

  39. Do they Conduct? • Conducting electricity is allowing charges to move. • In a solid, the ions are locked in place. • Ionic solids are insulators. • When melted, the ions can move around. • Melted ionic compounds conduct. • First get them to 800ºC. • Dissolved in water they conduct.

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