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# 5 Questions on Ionic/Covalent Bonding

(See attached file for full problem description with diagrams)

1. Which bonds below are polar and which are nonpolar? If a bond is polar, indicate which end is positive and which end is negative. (Pol Cov Bonds -Electronegativity )

C-S

F-C

N-O

Si-Br

Cl-C

2. Briefly explain why each Lewis formula attached is not reasonable.

3. A typical N-O single bond is 136 pm long and a typical N=O double bond is 115 pm long. The nitrate ion (shown below) has been found to contain three nitrogen-oxygen bonds with identical bond lengths of approximately 125 pm. Explain this observation in terms of resonance structures and bond order. (Bond Length & Order)

4. The 3 resonance structures for the SCO molecule are shown in the attachment.
a) Calculate the formal charge on each atom in each structure.
b) Which Lewis formula is the most reasonable?
c) Which Lewis formula is the least reasonable?
d) Explain your answers to parts b and c in terms of electronegativity and formal charges. (Formal Charge/Lewis Formulas)

5. The phosphate ion contains a central phosphorus atom surrounded by 4 oxygen atoms. Calculate the formal charge on each atom in each structure. Which Lewis formula is the most reasonable? Which Lewis formula is the least reasonable? Explain your answers to parts and in terms of electronegativity and formal charges. (Formal Charge/Lewis Formulas)

Structure 1 Structure 2 Structure 3

#### Solution Preview

See the attached Word document for solutions.

1. Which bonds below are polar and which are nonpolar? If a bond is polar, indicate which end is positive and which end is negative. (Pol Cov Bonds -Electronegativity )

C-S

F-C

N-O

Si-Br

Cl-C

To answer these questions, look up the electronegativity value for each element on your Periodic Table. Then if the electronegativity values are fairly similar, the bond is nonpolar. If the electronegativity values are substantially different, then the bond is polar. ALWAYS, the more electronegative element will be the one with the partial negative charge and the less electronegative atom will have the partial positive charge.

C 2.5
S 2.5
The difference is 0. This bond is of nonpolar.

F 4.0
C 2.5
The difference is 1.5. This bond is quite polar. Fl is the more negative end.

N 3.0
O 3.5
The difference is 0.5. This bond is minimally polar with O being the more negative end. In fact, with such a small difference in electronegativity, we should probably just consider this bond nonpolar.

Si 1.8
Br 2.8
The difference is 1.0. This bond is polar where the Br is the more negative end.

Cl 3.0
C 2.5
The difference is 0.5. This is fairly nonpolar.

2. Briefly explain why each Lewis formula below is not reasonable.

Structure 1 Structure 2 Structure 3

Structure 1: Carbon will have 4 bonds, not five. Therefore, the C on the left makes no sense. If you remove one of the H atoms attached to it, then it'd be fine. In addition, the O atom should have a negative charge on it since it only has a single ...

#### Solution Summary

Solution attaches answers to these questions on polarity, electronegativity, formal charges and lewis structures attached as Word.

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