Chem 3350 – Period 2

Assessment test

Chapter 1  

Bonding,

Chemical Bonding

1.   Covalent

a.   valences,         H, = 1

C, = 4

N, = 3

O, = 2

X   = 1

b.   octet rule,

c.    single, double and triple bonds,

d.   drawing predicted structures using valence and octet rules along with single double or triple bonds

examples:  CH₂O, C₂H₄O₂ and others.

C.  Polar, non-polar Covalent bonding

i.      dipole

ii.    induced dipole

iii.  dipole moment

D.    Ionic

E.   Lewis Dot Structures

          examples:  methane, ethane, ethene, ethyne, formaldehyde, acetic acid

F.   Formal charges

subtract the # of valence electrons assigned to an atom in its bonded state from the number of valence electrons it has as a neutral free atom.

          Examples: NH_3, NH₄⁺   NO₂^{-1  SO₃-2}

G.  Resonance

H.   Structural representations,

          tetrahedral shape of carbon in methane and ethane.

          Ethene has different shape, ethyne also.

I.  Group Activities.  - 15 min.

A.   Write the electron dot structure of

(1)  CH₂O                       (b)  C₃H₆    

B.      What is the formal charge on nitrogen in NaNO₃?  How many oxygen atoms in this substance have a formal charge of 0?

C.      Give an example of a compound that has

(1)  at least 1 polar covalent bond.

(2)  ionic bonding

(3)  has polar bonds but has a dipole moment of 0

(4)  is nonpolar

a.  Concept of resonance

b.  Concept of isomers

c.  Representation of Structural formulas

1.  Dash structural formulas:  ethane, propene,  butyne, isobutane

     Free rotation, different CONFORMATIONS.  (bring models)

d.  Tetrahedral shapes for single bonded carbons

e.  Condensed structural formulas.

f.   Cyclic molecules

g.  Bond-Line formulas

h.  3-D formulas

Problem Assignment:  Write resonance structures for the following

  ..

a.  CO₃^-2               b.  CH₃OSO₂                 c.  CH₃CO₂^-         

d.  CH₃CHCOCH₃         

(a)  C₄H₆O₂                                                                            (b)  CH₃-C₃H₅                       

         H  H   H  H 

2.   Draw an isomer of  H-C--C--C--C-H

                                             H  H   H  H 

3.  Draw 2 reasonable resonance structures for

(a)  CH₃CO₂^-                                                                                                  (b)  NO₃^-

4.  How many electrons are involved in a carbon to carbon triple bond? ______

5.  Indicate whether the following molecules have nonpolar, polar or ionic bonding.

a.  I₂     ________________            b.  HI________________   c.  OF₂_______________

6.  Using appropriate valence and octet rules draw reasonable electron dot structures for the following.

a.   CO₂                                  b.  C₂H₄O₂                              c.  HNO₃

7.  What is the formal charge on P in H₃PO₄?_________

     What is the formal charge on S in SO₂^-2? __________

8.  How many valence electrons are present in an atom of Br? __________

9.  What causes a bond to be polar?___________________________________________________

1. Indicate whether the following molecules have nonpolar, polar or ionic bonding.

a.  H₂O________________            b.  H₂________________   c.  F₂_______________

2.  Using appropriate valence and octet rules draw reasonable electron dot structures for the following.

a.   SO₂                                   b.  C₂H₄O                               c.  HNO₂

3.  What is the formal charge on S in H₂SO₄?_________

     What is the formal charge on N in NO₃^-? __________

4.  How many valence electrons are present in an atom of Ne? __________

5.     What causes a bond to be nonpolar?________________________________________________

6.  Draw dash and bond line formulas for the following

(a)  C₃H₆O                                                                              (b)  CH₃-C₄H₇                       

         H  H   H  H  H

7.   Draw an isomer of  H-C--C--C--C--C-H

                                             H  H   H  H  H

8.  Draw 2 reasonable resonance structures for

(a)  SO₃                                                                                                             (b)  CO₃^-