CHEM2004                                                                                                    Name___________________________

Exam 1                                                                                                            Fall 2006

 

1.         Write the valence configuration and the prepared for bonding configuration for each element/ ion below:            (10 points)

 

                        valence                                                                       prepared for bonding

a)  Se

 

 

b)  P

 

 

c)  Kr

 

 

d)  Mg

 

 

e) Ca⁺²

 

 

2.         Explain why carbon has a higher heat of atomization than sulfur.    (4 points)

  

3.         For the two elements below, list (A) the minimum oxidation number, (B) maximum oxidation number and (C) the common (+) oxidation number.                     (6 points)

 

(A)                   (B)                   (C) 

Hf -

 

Se -

 

4.         Draw or describe the allotropes of carbon.  Be sure to label the allotropes.     (6 points)

  

5.         Why does radon have a higher boiling point than krypton?                        (4 points)

  

6.         Give the element that best fits the description below:         (5 points)

 

a)         colorless diatomic gas ______________________________

 

b)         most reactive metal __________________________

 

c)         noble gas most likely to form compounds _____________________

 

d)         nonmetal that is liquid at 0^o C ______________

 

e)         yellow green gas ____________________________

 

7.         List the physical properties of nonmetals.    (5 points)

  

8.         For S, a) write the prepared for bonding configuration and tell the number of bonds expected for this element and b) does this explain the stable allotrope of S?  Draw the structure.         (8 points)

 

9.         Explain using drawings and M.O. theory, why metals are conductors and nonmetals are insulators.  How do semiconductors fit your explanation?  How many bonding M.O.'s do you expect for 1 mole of Cd atoms using p-orbitals?  (10 points)

   

10.       Define catenation.  Draw or give the formula for 2 cationic catenates of sulfur.    (4 points)

 

11.       The newly discovered element Dragonium (Dg) has a prepared for bonding configuration such that there are 4 unpaired electrons.  Calculate the BDE for a) an allotrope with 4 single bonds, b) an allotrope with 2 single bonds and 1 double bond, and c) an allotrope with 2 double bonds.  Based on covalent bond energies, determine which allotrope (a, b or c) Dg would be adopt.  The sigma BE is 200 kJ/mol and the pi BE is 100 kJ/mol.   (12 points)