Advanced Inorganic Chemistry

Test 2 Over Chapter 3

Name:  ________________________                                                                        April 14, 2017

49 possible

1.     (16 pts)    The last page of this test contains a flowchart for figuring out point groups.  To what point groups do the following belong?  (Models are available.)

a) SiCl4,

Td

b) H–H 

Dh

-1 pt for C∞v

c)      PCl5,

D3h

d)      POCl3,

C3v

 

2.   (7 pts)  The molecule on the right contains only three symmetry elements.  One of them is the identity element. 

a)      What are the other two?  (A model is available.)            S4 and C2         4 pts

b)      Is the molecule chiral?  Give a reason.

No; molecules that contain an axis of improper rotation are not chiral. 3 pts

-1 pt if yes, and no S4 in part a.

 

The following questions refer to the molecule on the right.  (The arrangement of the rings is shown below the structure.)

3.   (2 pts)  The electric dipole moment along the z-axis is

a)      non-zero.

b)      zero because the molecule has a center of inversion.  -1 pt

c)      zero because the z-axis is perpendicular to a mirror plane.

4.   (2 pts)  The electric dipole moment along the x-axis is

a)      non-zero.

b)      zero because the molecule has a center of inversion

c)      zero because the z-axis is perpendicular to a mirror plane.

d)      zero because the x-axis is perpendicular to an axis of rotation.

5.   (2 pts)  Is the molecule polar?   No

This page:  27 pts


 

6.   a) (4 pts)  The NO2- ion, , has 2p orbitals on the oxygens that can overlap with orbitals on the nitrogen. From the two p orbitals on oxygen shown, one of the two symmetry-adapted linear combinations (SALCs) that can be constructed from these two atomic orbitals is shown.  Sketch the other one (the two SALCs just differ in the sign of the wavefunction).


One is shown; the other looks like this: 

a)       (8 pts)   Indicate the symmetry type of each of these fragment orbitals in the C2v point group.  (The character table is provided below.)

C2v

E

C2

sv(xz)

sd(yz)

 

 

  A1

1

1

1

1

  z

  x2, y2, z2

  A2

1

1

-1

-1

  Rz

  xy

  B1

1

-1

1

-1

  x, Ry

  xz

  B2

1

-1

-1

1

  y, Rx

  yz

Symmetric:   1           1           1           -1    } this is symmetry type A1

Asymmetric: 1           -1          1           -1    } this is symmetry type B1

b)       (10 pts)       Which orbitals on the nitrogen (including d orbitals) have the same symmetry as your fragment orbitals?

Symmetric ligand group orbital:  s, pz, and dz2 (and, dx2-y2) orbitals have this symmetry.

Asymmetric ligand group orbital:  px and dxz orbitals have this symmetry.

This page:  22 pts


 

Point Group Flow Chart