The Chemistry Workshop          Honors Chemistry           Homework 5/11 - 5/21

Monday, May 11--Read section 15.1 and answer these questions.

1.  Define or describe these terms:  Valence Electrons, Electron Dot Structures, Octet Rule, cation, anion

2.  Study Table 15.1. 

        (a) Carbon has 6 electrons.  Why are there only 4 dots around the C in Table 15.1?

        (b) Why do O, S, & Se all have the same number of dots around them?

3.  Many atoms either gain or lose electrons to get an octet.  How many electrons will be gained or lost  by the following atoms?  (for your answer, say "gain 3", or ""lose 1")  (a) Mg     (b) S     (c) Br     (d) K

4.  Explain why transition metals form a "pseudo"-noble-gas electron configuration.  In your explanation, use cadmium as your example.  Go through the same arguments as the book did for silver.

5.  Explain why it is a good general statement to say "Metals tend to lose electrons, while non-metals tend to gain electrons."

6.  Write electron configurations for each of the following ions:

      (a) Sr²⁺      (b) Sr²⁺ has the same number of valence electron as which noble gas?

      (c) Se^2-      (b) Se^2- has the same number of valence electron as which noble gas?

      (e) Sc³⁺                  (f) Sc³⁺ has the same number of valence electron as which noble gas?

      (g) I^-           (h) I^- has the same number of valence electron as which noble gas?

Tuesday, May 12--Read sections 15.1 and 15.2 and answer these questions.

7.  Study figure 15.5.  Complete energy diagrams, like those in figure 15.5, for these transition metals:

      (a) Au & Au⁺     (b) Fe & Fe³⁺     (c) Ti & Ti⁴⁺

8.  Study figure 15.6.  Complete energy diagrams, like those in figure 15.6, for these atoms:

      (a) Br & Br^-     (b) S & S^2-     (c) N & N^3-

9.  Describe an Ionic Bond.

10. Study figure 15.7.  When writing formulas for ionic compounds, why must the number of positive charges equal the number of negative charges?

Read CHeMath on page 420 and answer questions 11-14.

11. (a) What is a Chemical Formula ?  (b) What does the chemical formula tell you about the shape of a molecule?

12. (a) What does a Structural Formula do for you?   (b) How does a Lewis Structure do this?  

        (c) How does a Bond-Line Structure do this?  (d) How does a Wedge Structure do this? 

        (e) Do any of these show the 3-dimensional structure of a molecule?

        (f) Draw Lewis, Bond-Line & Wedge structures for ammonia, NH₃.

13. (a) What is a Ball-and-Stick Model ?  (b) What does the chemical formula tell you about the shape of a molecule?

14. (a) What is a Space-Filling Model ?  (b) Why are they considered the most realistic of the models?

15. Study Sample Problem 15-1 and work practice problems 7 & 8. 

Use electron dot structures to predict the formulas of the ionic compounds formed from (a) Al & S     (b) Sr & F.  Your answer should look like the bottom part of the sample problem.

Wednesday, May 13--Read sections 15.2 & 15.3 and answer these questions.

16. Describe the structure of most ionic compounds at room temperature.

17. (a) What is a Crystal ?     (b) Describe the structure of NaCl.

18. Study figure 15.8.  Describe the crystals shown there.  Be sure to focus on the visible differences between crystals.

19. Study figure 15.9.  (a) Describe the differences in crystal structure between NaCl and CsCl.   (b) Compare the number of chloride ions that surround each sodium ion to the number of chloride ions that surround each cesium ion.

20. Study figures 15.9 & 15.10   (a) What is Coordination Number ?  

        (b) What is the coordination number of sodium ion in NaCl? 

        (c) What is the coordination number of chloride ion in NaCl?    

        (d) What is the coordination number of titanium ion in TiO₂?    

        (e) What is the coordination number of oxide ion in TiO₂?    

21. (a) Describe X-Ray Crystallography.    (b) How is it used to study the internal structure of ionic crystals?

22. (a) Do ionic crystals conduct electricity?    

(b) How about molten ionic compounds?    

(c) How about solutions of ionic compounds?    

(d) Why must ionic compounds be molten or in solution to conduct electricity?

23. What determines the crystal structure of an ionic compound?

Thursday, May 14--Read sections 15.2 & 15.3 and answer these questions.

24. Study figures 15.13 & 15.14 and the text.

        (a) Describe the structure of metals.  (b) How is this really really different from the structure of ionic compounds?

        (c) How would you describe a Metallic Bond?

        (d) How does this structure explain why metal deforms when stressed, while ionic crystals break?  

        (e) How does this structure explain why metals are good conductors of electricity?

        (f) Differentiate between Ductility and Malleability, two properties of metals.

25. Do metals form crystal structures? 

26. Study figures 15.15 & 15.16.  Differentiate between these crystal structures:

        (a) Body-Centered Cubic     (b) Face-Centered Cubic     (c) Hexagonal Close-Packed

27. (a) What is an alloy?    (b) How are alloys made?   (c) What is brass     (d) What is bronze?

28. Study Table 15.3  What is the composition of these well-known alloys?

        (a) Surgical Steel     (b) Stainless Steel     (c) Sterling Silver      (d) "Coin" Silver     (e) Cast Iron

29. Differentiate between ferrous and non-ferrous alloys.

30. Steel is mostly iron & carbon, with other elements added to it. 

        (a) Name 6 common additives to steel.     (b) Why add these other elements?  What does it do for the steel?

31. Differentiate between Substitutional Alloys and Interstitial Alloys.

Friday, May 15--Read "Chemistry Serving the Consumer--When Water is Hard to Deal With" and answer these questions.

32. (a) What is Hard Water?   (b) List the ions usually found in hard water.   (c) How do these ions get in the water?

33. Describe 2 annoying consequences of living in a community with hard water.

34. (a) Describe a Water Softener.      

(b) What do they do to remove the hardness from water?    

(c) Describe the inside parts of a water softener.    

(d) How is the zeolite matrix treated prior to installing the water softener in your home?    

(e) What happens as the hard water passes through the zeolite matrix?     (f) Why does this happen?

35. (a) Water from a water softener often tastes salty.  WHY       (b) Are there any problems with drinking water containing Na⁺?

36. (a) About how long can you expect a water softener to last?     (b) Describe how water softeners are "recharged".

37. Define or describe the Chapter 15 terms:  Valence Electron, Electron Dot Structure, Cation, Anion, Octet Rule, Ionic Bond, Crystal, Coordination Number, Metallic Bond, Alloy.

Monday, May 18--Read 16.1 and consult your class notes as you answer these questions. 

***Note: In molecular formulas for electron dot structures, the central atom is underlined***

1.  How are molecular compounds, such as HCl, different from ionic compounds like NaCl?

2.  Why is a "tug of war" a good analogy for a covalent bond?

3.  What is a covalent bond?

4.  Molecular compounds form molecules.  What do Ionic compounds form?

5.  Study figure 16.2.  What are they trying to show in this figure?

6.  Where in the Periodic Table are you likely to find the atoms that form covalent bonds?

7.  Read the CHEMath section on page 441.  Study Sample Problem 16-1 and work practice problems 1 & 2.

        Draw electron dot structures of these molecules:  F₂   Cl₂   H₂S    NH₃   CH₄   PCl₃   HBr   OF₂    NI₃

Tuesday, May 19--Read 16.1 and consult your class notes as you answer these questions. 

***Note: In molecular formulas for electron dot structures, the central atom is underlined***

8.  (a) What is a double bond?     (b) What is a triple bond?

9.  Draw electron dot structures of these molecules:  N₂   HCN   CO₂    CS₂   H₂CO   CO    O₃

10. What is a Coordinate covalent bond?

11. What is a Polyatomic ion?

12. Study Sample Problems 16-2 & 16-3 and work practice problems 3-6.

        Draw electron dot structures of these polyatomic ions:  SO₃^2-   CN^-   CO₃^2-    NO₂^-   ClO₃^-  ClO^-   ClO₄^-

13. What is a Bond Dissociation Energy?

14. Study Table 16.3.  Rank these bond energies from Strongest ==> Weakest:

        C-C double bonds, H-H bonds, C-C single bonds, C-O double bonds, C-N Single bonds, C-C triple bonds, C-O Single bonds

Wednesday, May 20--Read 16.1 & 16.2 and consult your class notes as you answer these questions.

Note: In molecular formulas for electron dot structures, the central atom is underlined.

15. (a) What are Resonance Structures?  Draw resonance structures for these ions & molecules:   NO₂^-   SO₃    CO₃^2-

16. What does it mean to say that something is an exception to the octet rule?

        (a) Draw the electron dot structure for NO₂.  (b) Why is this an "exception" to the octet rule?

        (c) Draw the electron dot structure for BH3.  (d) Why is this an "exception" to the octet rule?

        (e) Draw the electron dot structure for PF₅.  (f) Why is this an "exception" to the octet rule?

        (g) Draw the electron dot structure for SF6.  (h) Why is this an "exception" to the octet rule?

17. Explain the difference between an Atomic Orbital and a Molecular Orbital.

18. Describe the difference between Bonding and Antibonding molecular orbitals.

19. Study figure 16.11.  Explain why electrons in H₂ occupy the bonding orbitals rather than the antibonding orbitals.

20. Draw an energy diagram to show why there is no such thing as He₂.

21. (a) What is a Sigma Bond?     (b) What is a Pi Bond?

        (c) Show how overlap of an "s" atomic orbital with another "s" atomic orbital makes a Sigma bond.

        (d) Show how overlap of an "s" atomic orbital with a "p" atomic orbital makes a Sigma bond.

        (e) Show how overlap of a "p" atomic orbital with another "p" atomic orbital makes a Pi bond

Thursday, May 21--Read 16.2 & 16.3 and consult your class notes as you answer these questions.

Note: In molecular formulas for electron dot structures, the central atom is underlined.

22. (a) What does VSEPR stand for?     (b) What is the premise behind VSEPR theory?

23. Study figures 16.14 & 16.15.  Recreate & fill in the table below.