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CHAPTER 8

CHAPTER 8. Compounds and Molecules. 8.1 Ionic Compounds. In early chapters we discussed physical and chemical properties. In early chapters we discussed physical and chemical properties. In later chapters we discussed atom structures and chemical bonding.

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CHAPTER 8

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  1. CHAPTER 8 Compounds and Molecules 8.1 Ionic Compounds

  2. In early chapters we discussed physical and chemical properties

  3. In early chapters we discussed physical and chemical properties In later chapters we discussed atom structures and chemical bonding

  4. Atom structures andchemical bonding Physical and chemicalproperties How are they related?

  5. Ionic compounds (like table salt, NaCl) First we address ionic compounds Atom structures andchemical bonding Physical and chemicalproperties How are they related?

  6. Molecular compounds (like DNA) Then we will address molecular compounds Atom structures andchemical bonding Physical and chemicalproperties How are they related?

  7. Structure of NaCl We have seen that in an ionic salt each atom interacts with all its neighbors. Each chloride ion is attracted to all nearby sodium ions Each sodium ion is attracted to all nearby chloride ions

  8. In any ionic crystal, the ratio of positive ions to negative ions must allow for all of the positive charge to cancel out all of the negative charge. Lead(II) sulfide (PbS) Aluminum oxide (Al2O3) Copper(II) sulfate (CuSO4) Pb2+ and S2– (+2) and (–2) 2Al3+ and 3O2– (+6) and (–6) Cu2+ and SO42– (+2) and (–2)

  9. Properties The ionic structure leads to the following physical properties: Ionic substances are solid at room temperature To be in a liquid state, there must be enough energy for each atom to break free from the attractive forces from its neighbors.

  10. Properties The ionic structure leads to the following physical properties: Ionic substances are solid at room temperature Ionic substances have very high melting points To be in a liquid state, there must be enough energy for each atom to break free from the attractive forces from its neighbors.

  11. Properties The ionic structure leads to the following physical properties: Ionic substances are solid at room temperature Ionic substances have very high melting points Ionic substances are hard The interconnected network of bonds holds the entire crystal together

  12. Properties The ionic structure leads to the following physical properties: Ionic substances are solid at room temperature Ionic substances have very high melting points Ionic substances are hardbut brittle Ionic substances are brittle, which means they break

  13. Properties When melted or dissolved, ions are free to move around, making it possible for an ionic solution to conduct electricity Ions dissolved in water move in random directions by colliding with water molecules Overall ion movement toward the electrodes creates an electrical current

  14. Polyatomic ions An ion does not have to be a single atom. An ion can be a small molecule with a charge. a monatomic ion a polyatomic ion

  15. Polyatomic ions Calcium carbonate, CaCO3 The calcium ion contributes a +2 charge (Ca2+) The CO3 molecule needs two extra electrons. Draw

  16. The two oxygens now have a –1 charge, giving the whole molecule a –2 charge Polyatomic ions The carbonate ion switches among these three versions.

  17. Ammonium sulfate (NH4)2SO4 is made from two polyatomic ions

  18. Now we will learn how to: • Writeformulas for ionic compounds • Write names for ionic compounds • Name ions with transition metals

  19. Writing formulas Balancing positive and negative charge in ionic formula writing

  20. Writing formulas Balancing positive and negative charge in ionic formula writing

  21. Writing formulas Write the correct formulas for the compounds that will form using the following ion pairs: Mg2+ and Cl–, Na+ and S2–, Al3+ and O2–.

  22. Writing formulas Write the correct formulas for the compounds that will form using the following ion pairs: Mg2+ and Cl–, Na+ and S2–, Al3+ and O2–. Asked: Ionic formulas for the three different ionic substances Given: The charges on all of the ion pairs Relationships: The positive ions will combine with the negative ions in a ratio so that the positive and negative charges from the ions will be equal.

  23. Writing formulas Write the correct formulas for the compounds that will form using the following ion pairs: Mg2+ and Cl–, Na+ and S2–, Al3+ and O2–. Asked: Ionic formulas for the three different ionic substances Given: The charges on all of the ion pairs Relationships: The positive ions will combine with the negative ions in a ratio so that the positive and negative charges from the ions will be equal. Solve: For each Mg2+ we need two Cl– (+2 – 1 – 1 = 0) and the formula is MgCl2.

  24. Writing formulas Write the correct formulas for the compounds that will form using the following ion pairs: Mg2+ and Cl–, Na+ and S2–, Al3+ and O2–. Asked: Ionic formulas for the three different ionic substances Given: The charges on all of the ion pairs Relationships: The positive ions will combine with the negative ions in a ratio so that the positive and negative charges from the ions will be equal. Solve:For each Mg2+ we need two Cl– (+2 – 1 – 1 = 0) and the formula is MgCl2. For each S2– we need two Na+ (–2 + 1 +1 = 0) and the formula is Na2S.

  25. Writing formulas Write the correct formulas for the compounds that will form using the following ion pairs: Mg2+ and Cl–, Na+ and S2–, Al3+ and O2–. Asked: Ionic formulas for the three different ionic substances Given: The charges on all of the ion pairs Relationships: The positive ions will combine with the negative ions in a ratio so that the positive and negative charges from the ions will be equal. Solve:For each Mg2+ we need two Cl– (+2 – 1 – 1 = 0) and the formula is MgCl2. For each S2– we need two Na+ (–2 + 1 +1 = 0) and the formula is Na2S. To balance charges between Al3+ and O2– we need to multiply Al by 2 and O by 3 [2(+3) + 3(–2) = 0]. The formula is Al2O3.

  26. Writing formulas Polyatomic ions represent a single unit with a charge just like single-atom ions

  27. Writing formulas Writing formulas with polyatomic ions The chlorate ion (ClO3–) is made by covalently bonding chlorine to three oxygens and adding an extra electron To indicatemore than onechlorate,parenthesesmust be used

  28. Writing formulas Write the correct formulas for the compounds that will form using the following ion pairs: Mg2+ and SO42–, Ca2+ and PO43–, and NH4+ and S2–.

  29. Writing formulas Write the correct formulas for the compounds that will form using the following ion pairs: Mg2+ and SO42–, Ca2+ and PO43–, and NH4+ and S2–. Asked: Ionic formulas for three different ionic substances listed Given: The charges on all of the ion pairs Relationships: The positive ions will combine with the negative ions in a ratio so that the positive and negative charge from the ions will be equal.

  30. Writing formulas Write the correct formulas for the compounds that will form using the following ion pairs: Mg2+ and SO42–, Ca2+ and PO43–, and NH4+ and S2–. Asked: Ionic formulas for three different ionic substances listed Given: The charges on all of the ion pairs Relationships: The positive ions will combine with the negative ions in a ratio so that the positive and negative charge from the ions will be equal. Solve: For each Mg2+, we need one SO42– (+2 – 2 = 0) and the formula is MgSO4.

  31. Writing formulas Write the correct formulas for the compounds that will form using the following ion pairs: Mg2+ and SO42–, Ca2+ and PO43–, and NH4+ and S2–. Asked: Ionic formulas for three different ionic substances listed Given: The charges on all of the ion pairs Relationships: The positive ions will combine with the negative ions in a ratio so that the positive and negative charge from the ions will be equal. Solve:For each Mg2+, we need one SO42– (+2 – 2 = 0) and the formula is MgSO4.To balance charges between Ca2+ and PO43–, multiply Ca by 3 and PO4 by 2: [3(+2) + 2(–3) = 0]. The formula is Ca3(PO4)2.

  32. Writing formulas Write the correct formulas for the compounds that will form using the following ion pairs: Mg2+ and SO42–, Ca2+ and PO43–, and NH4+ and S2–. Asked: Ionic formulas for three different ionic substances listed Given: The charges on all of the ion pairs Relationships: The positive ions will combine with the negative ions in a ratio so that the positive and negative charge from the ions will be equal. Solve:For each Mg2+, we need one SO42– (+2 – 2 = 0) and the formula is MgSO4.To balance charges between Ca2+ and PO43–, multiply Ca by 3 and PO4 by 2: [3(+2) + 2(–3) = 0]. The formula is Ca3(PO4)2.For each S2– we need two NH4+. The formula is (NH4)2S.

  33. Writing names With monatomic ions:

  34. Writing names Names for polyatomic ions

  35. Writing names With monatomic ions: With polyatomic ions: Draw

  36. Naming transition metal ions Most transition metals can have different charges A Roman numeral indicates the charge on a positive ion Check whether a Roman numeral is necessary for elements in the highlighted parts of the periodic table

  37. Naming transition metal ions Consider PbCl2 Check the common ions table

  38. Naming transition metal ions Consider PbCl2 Check the common ions table Use the negative ion to determine the charge on lead

  39. Naming transition metal ions Consider PbCl2 Check the common ions table Use the negative ion to determine the charge on lead With only one Pb ion, and a total charge of +2 needed, the Pb ion must be lead(II)

  40. Naming transition metal ions Consider ZnSO4 Check the common ions table

  41. Naming transition metal ions Consider ZnSO4 Check the common ions table Zn only forms a +2 ion No Roman numeral is needed

  42. Write the names for each of the following formulas: CaCl2, Zn(NO3)2, Fe3(PO4)2.

  43. Write the names for each of the following formulas: CaCl2, Zn(NO3)2, Fe3(PO4)2. Asked: Names for the formulas above Given: Three formulas and a common ion table Relationships: The name of each formula is constructed form the name of the ions. If the negative ion is a single atom, modify the name of the element to end in “-ide.” If the positive ion might form multiple charges, make sure to use a Roman numeral in the name.

  44. Write the names for each of the following formulas: CaCl2, Zn(NO3)2, Fe3(PO4)2. Asked: Names for the formulas above Given: Three formulas and a common ion table Relationships: The name of each formula is constructed form the name of the ions. If the negative ion is a single atom, modify the name of the element to end in “-ide.” If the positive ion might form multiple charges, make sure to use a Roman numeral in the name. Solve: CaCl2 is calcium chloride.

  45. Write the names for each of the following formulas: CaCl2, Zn(NO3)2, Fe3(PO4)2. Asked: Names for the formulas above Given: Three formulas and a common ion table Relationships: The name of each formula is constructed form the name of the ions. If the negative ion is a single atom, modify the name of the element to end in “-ide.” If the positive ion might form multiple charges, make sure to use a Roman numeral in the name. Solve:CaCl2 is calcium chloride.Zn(NO3)2 is zinc nitrate.

  46. Write the names for each of the following formulas: CaCl2, Zn(NO3)2, Fe3(PO4)2. Asked: Names for the formulas above Given: Three formulas and a common ion table Relationships: The name of each formula is constructed form the name of the ions. If the negative ion is a single atom, modify the name of the element to end in “-ide.” If the positive ion might form multiple charges, make sure to use a Roman numeral in the name. Solve:CaCl2 is calcium chloride.Zn(NO3)2 is zinc nitrate. Fe3(PO4)2 is iron(II) phosphate.

  47. The ionic structure leads to the following physical properties: Ionic substances are solid at room temperature Ionic substances have very high melting points Ionic substances are hard but brittle Overall ion movement creates an electrical current

  48. We learned how to: Writeformulas for ionic compounds Write names for ionic compounds Name ions with transition metals a polyatomic ion

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