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Chapter 7 Notes Chemical Formulas & Chemical Compounds

Chapter 7 Notes Chemical Formulas & Chemical Compounds. West Valley High School General Chemistry Mr. Mata. Standard 3d. D etermine the molar mass of a molecule from its chemical formula and atomic masses. Essential Question.

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Chapter 7 Notes Chemical Formulas & Chemical Compounds

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  1. Chapter 7 Notes Chemical Formulas & Chemical Compounds West Valley High School General Chemistry Mr. Mata

  2. Standard 3d • Determine the molar mass of a molecule from its chemical formula and atomic masses.

  3. Essential Question • How do you write chemical formulas for chemical compounds using a set of standard rules?

  4. Ions • Ions: atom (groups of atoms = polyatomic ions) that have a charge. • Number of protons (p+) is not equal to the number of electrons (e-). p+≠ e- • Cation: A positive ion • Mg2+, NH41+ • Anion: A negative ion • Cl1 -, SO42 - • Ionic Bonding: Force of attraction between oppositely charged ions.

  5. Predicting Ionic Charges Group 1: Lose 1 e- to form +1 ions H+1 Li+1 Na+1 K+1

  6. Predicting Ionic Charges Group 2: Loses 2 e-’s to form +2 ions Be+2 Mg+2 Ca+2 Ba+2 Sr+2

  7. Predicting Ionic Charges Group 13: Loses 3 e-’s to form +3 ions B+3 Al+3 Ga+3

  8. Predicting Ionic Charges Group 14: Lose 4 e-’s or gain 4 e-’s? Neither! Group 14 elements rarely form ions.

  9. Predicting Ionic Charges Nitride N-3 Group 15: Gains 3 e-’s to form -3 ions P-3 Phosphide As-3 Arsenide

  10. Predicting Ionic Charges Oxide O-2 Gains 2 e-’s to form -2 ions Group 16: S-2 Sulfide Se-2 Selenide

  11. Predicting Ionic Charges F-1 Fluoride Br-1 Bromide Group 17: Gains 1 e- to form -1 ions Cl-1 Chloride I-1 Iodide

  12. Predicting Ionic Charges Group 18: Stable Noble gases do not form ions!

  13. Predicting Ionic Charges Many transition elements have more than one possible ionic charge. Groups 3 - 12: Iron(II) = Fe+2 Iron(III) = Fe+3

  14. Predicting Ionic Charges Some transition elements have only one possible ionic charge. Groups 3 - 12: Zinc (II) = Zn+2 Silver (I) = Ag+1

  15. Writing Ionic Compound Formulas Example: Magnesium carbonate 1. Write the formulas for the cation and anion, including CHARGES! Mg+2 CO3-2 2. Check to see if charges are balanced. They are balanced! MgCO3

  16. Writing Ionic Compound Formulas Example: Iron(III) chloride 1. Write the formulas for the cation and anion, including CHARGES! Fe+3 Cl-1 2. Check to see if charges are balanced. 3 3. Balance charges , if necessary, using subscripts. Not balanced! FeCl3

  17. Writing Ionic Compound Formulas Example: Barium nitrate 1. Write the formulas for the cation and anion, including CHARGES! ( ) 2. Check to see if charges are balanced. Ba+2 NO3- 2 Not balanced! 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Ba(NO3)2

  18. Writing Ionic Compound Formulas Example: Ammonium sulfate 1. Write the formulas for the cation and anion, including CHARGES! ( ) NH4+ SO4-2 2. Check to see if charges are balanced. 2 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced! (NH4)2SO4

  19. Writing Ionic Compound Formulas Example: Aluminum sulfide 1. Write the formulas for the cation and anion, including CHARGES! 2. Check to see if charges are balanced. Al+3 S-2 2 3 3. Balance charges , if necessary, using subscripts. Not balanced! Al2S3

  20. Writing Ionic Compound Formulas Example: Zinc hydroxide 1. Write the formulas for the cation and anion, including CHARGES! ( ) 2. Check to see if charges are balanced. Zn+2 OH- 2 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced! Zn(OH)2

  21. Writing Ionic Compound Formulas Example: Aluminum phosphate 1. Write the formulas for the cation and anion, including CHARGES! 2. Check to see if charges are balanced. Al3+ PO43- They ARE balanced! AlPO4

  22. TOP SECRET!!! • DO NOT REVEAL THIS SECRET TECHNIQUE TO ANY OTHER CHEMISTRY CLASS!!!

  23. Criss-Cross Shortcut Method Ex: Na+1 S2- Na 2 S 1 = Na2S sodium sulfide Ex: Mg2+ Br-1 Mg1 Br2 = MgBr2 magnesium bromide

  24. Criss-Cross Shortcut Method Example: Al 3+ S 2- Al2 S3 = Al2S3 aluminum sulfide Example: Al 3+ CO3 2- Al2 (CO3)3 = Al2(CO3)3 aluminum carbonate

  25. Naming Ionic Compounds • 1. Cation first, then anion • 2. Monatomic cation = name of element • Ca2+ = calciumion • 3. Monatomic anion = root + -ide • Cl-1 = chloride • CaCl2= calcium chloride

  26. Naming Ionic Compounds(continued) Metals with multiple oxidation states • - some metals form more than one cation. • - use Roman numeralin name. • PbCl2 • Pb2+is cation • PbCl2 = lead(II) chloride

  27. Naming Binary Compounds • -Compounds between two nonmetals. • -First element in formula is named first. • -Second element named as if it were an anion. • - Use prefixes. • - Only use mono on second element - P2O5 = diphosphorus pentoxide CO2 = carbon dioxide CO = carbon monoxide N2O = dinitrogen monoxide

  28. Calculating Formula Mass Calculate the formula mass of magnesium carbonate, MgCO3. 24.31 g + 12.01 g + 3(16.00 g) = 84.32 g

  29. Calculating Percentage Composition Calculate the percentage composition of magnesium carbonate, MgCO3. From previous slide: 24.31 g + 12.01 g + 3(16.00 g) = 84.32 g 100 %

  30. Empirical formula: lowest whole number ratio of atoms in a compound. Molecular formula: true number of atoms of each element in the formula of a compound. Molecular: C6H12O6 H2O C12H22O11 Empirical: H2O CH2O C12H22O11

  31. Formulas for ionic compounds are ALWAYS empirical (lowest whole number ratio). Examples: NaCl MgCl2 Al2(SO4)3 K2CO3

  32. Empirical Formula Determination • Base calculation on 100 grams of compound. • Determine moles of each element in 100 grams of compound. • Divide each value of moles by the smallest of the values. • Multiply each number by an integer to obtain all whole numbers.

  33. Empirical Formula Determination Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid?

  34. Empirical Formula Determination(part 2) Divide each value of moles by the smallest of the values. Carbon: Hydrogen: Oxygen:

  35. Empirical Formula Determination(part 3) Multiply each number by an integer to obtain all whole numbers. Carbon: 1.50 Hydrogen: 2.50 Oxygen: 1.00 x 2 x 2 x 2 3 5 2 C3H5O2 Empirical formula:

  36. Chapter 7 SUTW Prompt • Describe the differences between writing chemical formulas for molecular compounds and ionic compounds. • Complete an 8-12 sentence paragraph using the SUTW paragraph format. Hilight using green, yellow, and pink. • Due Date: Monday, October 23, 2017 at beginning of your regular class. (Happy Mole Day!!!).

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