Chemistry 401

Intermediate Inorganic Chemistry

University of Rhode Island

Exam 1

October 7, 2009
open book, open notes

1. Find the electron configuration and ground state term symbol for a) Co3+; b) Rh2+; c) Pt2+; d) Gd3+; e) Pb2+. Use the rare gas notation for closed shells.

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2. Write the Lewis dot structure showing the formal charges, predict the structure including an estimate of all bond angles, and indicate the likely hybrid orbital on the central atom for the following: a) TeOF2; b) BrF4; c) ClO4; d) PF3.

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3. Draw a molecular orbital energy diagram for NO+. Find the bond order from your MO diagram and compare it to that predicted from the Lewis structure. Give the electron configuration.

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4. In a recent paper by R. F. See in the Journal of Chemical Education an analysis of the octet rule vs. the formal charge rule for Lewis structures was done. A theoretical description of the bond order using experimental bond lengths was compared to the two ways to draw Lewis structures. The table below gives a sampling of the results.

Compound

Octet Rule Bond Order

Formal Charge Rule Bond Order

Theoretical Bond Order

NO2

1.5

2

1.53

PO2

1.5

2

1.88

O3

1.5

2

0.95

SO2

1.5

2

1.80

NF3

1

1

0.82

PF3

1

1

1.17

BCl3

1.33

1

1.02

AlCl3

1.33

1

1.03

Draw the two Lewis structures for NO2 and explain how the two different bond orders are found. Based on the data given, what conclusions can you come to about the best way to draw Lewis structures? Support your arguments using the data given.

Answer