Follow the instructions given for each section of this worksheet. You will need your periodic table, a chart of common polyatomic ions, and your wits to complete this homework.

Part I

1. When you look at the formula of a compound how can you tell whether it is a molecular compound or an ionic compound?
2. What is a diatomic molecule?
3. Which elements exist in pure form as diatomic molecules? (Remember, you must memorize these!)
4. What are some compounds that are diatomic molecules?
5. What is an allotrope? Give some examples.
6. How do electrolytes differ from non-electrolytes in their behavior when they dissolve in water?
7. Why don’t non-electrolyte solutions conduct electricity?
8. Why is the formula of a compound made of magnesium ions (Mg²⁺) and oxide ions (O^2–) written as MgO and not Mg₂O₂?
9. Explain why you can’t change the subscripts in the formulas of polyatomic ions like PO₄^3- or NH₄⁺.
10. When are parentheses necessary in writing the formulas of ionic compounds? Why are they used?
11. What is the meaning of the roman numerals after the names of some metal elements’ ions? For example, Fe²⁺ is called iron(II).
12. When writing the name of an ionic compound containing a metal ion which sometimes has one ionic charge and sometimes has another how do you know which ion name to use? For example, PbCO₃ and Pb(CO₃)₂ are different compounds with different names. What are their names and how did you figure it out?
13. Give the names of the binary acids: HF, HCl, HBr, HI.
14. What are oxyanions? Give four example ion names and formulas. Let the names illustrate the meaning of the suffixes used (-ite and -ate).
15. Write the name and formula of all four oxyanions of chlorine.
16. What are oxyacids? Give the name and formula of the oxyacids of chlorine and the oxyacids based on phosphate, sulfate, and nitrate.
    For each anion, write the name and formula of the acid formed by combination with H⁺ ion.
    • ClO^–
    • ClO₂^1–
    • ClO₃^1–
    • ClO₄^1–
    • PO₄^3–
    • SO₄^2–
    • NO₃^1–
17. What do the suffixes –ide, –ite, and –ate mean?
    • –ide
    • –ite
    • –ate

Part II

(a) Write the ionic form of each of the following elements, showing the charge you would expect it to have based on its location in the periodic table. (b) Then build a compound from those ions, writing a chemical formula. Also, (c) write the name of the compound. Remember, the total positive and negative charges must be equal so that the compound is neutrally charged.

18. Sodium, Iodine (example)
         Na⁺    I^-    NaI    Sodium Iodide
19. Calcium, Sulfur
20. Aluminum, Chlorine

21. Barium, Oxygen
22. Potassium, Sulfur
23. Strontium, Nitrogen

Part III

Name the following formulas, which may be elements, molecular compounds, ionic compounds, or acids.

24. AgNO₃
25. BaCrO₄
26. Mg(OH)₂
27. O₂F₂
28. ZnSO₄
29. K₂CO₃
30. Pb(NO₃)₂
31. MnCl₂
32. NiS
33. AlH₃
34. HClO₃
35. BaSO₃
36. H₂SO₄

37. PCl₅
38. SF₄
39. SF₆
40. Cl₂
41. PbCl₂
42. Sn(NO₂)₂
43. PCl₃
44. H₂O
45. CuNO₃
46. Ti₃(PO₄)₄
47. Si₃N₄
48. ClF₃
49. AsI₃

Part IV

Write formulas for the following names, which may be elements, molecular compounds, ionic compounds, or acids.

50. Lead(IV) Oxide
51. Phosphorus Pentachloride
52. Calcium Phosphate
53. Dinitrogen Tetrasulfide
54. Nitrous Acid
55. Copper(I) Oxide
56. Copper(II) Phosphide
57. Carbon Monoxide

58. Lead(II) Carbonate
59. Iodine Monobromide
60. Hydrobromic Acid
61. Xenon Tetrafluoride
62. Copper(II) Oxide
63. Chloric Acid
64. Carbon Disulfide
65. Oxygen