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Homework: Chemical Formulas I

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

Answer the following questions.

  1. Describe the process by which atoms become ions.
  2. Explain why atoms never lose or gain protons when they become ions.
  3. Do elements in groups 13 through 17 tend mostly to lose or gain electrons? Why?
  4. Do elements in groups 1 and 2 tend mostly to gain or lose electrons? Why?
  5. What is a diatomic molecule? Which elements exist in pure form as diatomic molecules?
  6. What are positive ions called? Negative ions?
  7. Describe an easy way to tell electrolytes apart from non-electrolytes.
  8. What is an allotrope? Give some examples.
  9. What are the differences between a molecular compound and an ionic compound?

Part II

For each of the following ions write down the total number of p+ and e-. For example: Na+ has 11 p+, 10 e-.

  1. K+
  2. As3-
  3. Fe2+
  4. Ca2+
  5. N3-
  1. Sc3+
  2. Sr2+
  3. Fe3+
  4. Cl-
  5. O2-


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Part III

(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.

  1. Sodium, Iodine (example)
         Na+    I-    NaI    Sodium Iodide
  2. Calcium, Sulfur
  3. Caesium, Bromine
  4. Aluminum, Chlorine
  5. Barium, Oxygen
  1. Magnesium, Fluorine
  2. Iron(III), Oxygen
  3. Potassium, Sulfur
  4. Strontium, Nitrogen
  5. Lithium, Phosphorus

Part IV

Name the following compounds.

  1. AgNO3
  2. BaCrO4
  3. Mg(OH)2
  4. ZnSO4
  5. K2CO3
  6. Pb(NO3)2
  7. MnCl2
  8. NiS
  9. AlH3

  1. NH4NO2
  2. Zn3(PO4)2
  3. KClO3
  4. (NH4)2CrO4
  5. CuSO4
  6. NH4Cl
  7. SrI2
  8. TiO2
  9. P4O10

Part V

Write formulas for the following compounds.

  1. Lithium Bromide
  2. Carbon Monoxide
  3. Aluminum Fluoride
  4. Mercury(II) Sulfate
  5. Barium Hydride
  6. Lead(IV) Oxide
  7. Calcium Phosphate
  8. Phosphorus Pentachloride
  1. Copper(I) Oxide
  2. Sodium Sulfide
  3. Dinitrogen Tetrasulfide
  4. Iodine Monobromide
  5. Beryllium Bromide
  6. Lead(II) Carbonate
  7. Cobalt(III) Chloride
  8. Xenon Tetrafluoride
This homework belongs with the Chemical Formulas and Compounds group activity.
Many problems were inspired by those at Mr. Basset’s Site.
Last updated: Mar 11, 2007        Home