(20 pts)  Write the electron dot structures for each of the following atoms/ions:
 
 

1.  S	2.  N	3.  Mg	4. Br	5. Kr
6. Sr+	7. At-	8. Sb3-	9. Ba+4	10. Cl+2

11. (4  pts)  Helium is a noble gas even though it does not have 8 valence electrons.  Explain why (be very specific).

12. (25 pts)  Complete the following table:
 
 

Element	Cl	S	Be	Rn	Cs
No. of Valence Electrons
Electron Dot Structure
No. of Electrons Lost or Gained
Which Noble Gas Will it Look Like?
Charge on the Ion

13 (3 pts)  Why do all of the elements in the first column of the periodic table tend to have a +1 charge in their ion form?

(6 pts)  Write the formula for the compounds that would be produced from the combination of the following atoms:

14.  Ca + F   15.  Rb + O   16.  Mg + N
 

For the following compounds draw the structural formula.  WARNING: To get full credit you must show all bonds (i.e. single, double, triple), all electrons, and all the angles between the atoms.

17.  (3 pts)  SiF4

18.  (3 pts)  NO₂-

19.  (3 pts)  PCl3

20.  (3 pts)  C2H2 (Hint: H-C-C-H)

21. (5 pts)  Describe in gruesome detail why an ionic bond forms between a metal and a non-metal.  In your explanations you may include pictures and you should discuss the octet rule.

22. (4 pts)  Why won't an ionic bond form between two or more non-metals?  Be very specific.

23. (5 pts)  Complete the structure of the following molecule showing all bonds, electrons and bond angles (NOTE: all of the electrons and bonds are not shown below.  You must add them!)

Ignore this problem.  There is not one like it on the test.

24. (3 pts)  If your house caught on fire and you only had time to save one thing from your room before it burned down, what would it be?

For answers 1-10, the number of dots surrounding the symbol is given:
 

1. 6
2. 5
3. 2
4. 7
5. 8
6. 1
7. 8
8. 8
9. 6
10. 5
11. All of the Noble Gases have filled energy levels.  Normally, to fill an energy level takes 8 (an octet) electrons.  However, because the first energy level of Helium is its highest occupied energy level only 2 electrons are required to fill this level.
12. All answers are listed going down the columns    Cl: 7, 7 dots, 1 gained, Ar, -1    S: 6, 6 dots, 2 gained, Ar, -2    Be: 2, 2 dots, 2 lost, He, +2    Rn: 8, 8 dots, 0, Rn, 0    Cs: 1, 1 dot, 1 lost, Xe, +1
13. All elements in the first column have one valence electron.  In order to gain a full octet, it is likely that they will lose this one electron giving them a +1 charge.
14. CaF2
15. Rb2O
16. Mg3N2

21. Metals tend to lose electrons to gain a full octet.  Non-metals tend to gain electrons to gain an octet.  Therefore, metals tend to transfer their electrons to non-metals resulting in oppositely charged ions which then stick together to form an ionic bond.
22. Non-metals tend to gain electrons to complete their octet.  Two non-metals would NOT want to transfer electrons, because both tend to GAIN electrons.  Therefore, they will not form an ionic bond.