homework1 key
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Chem452/552 Inorganic Chemistry ------------------Point Group Name: _________________ 1. Indicate by ci rcling whether each of the following statements is true or is false.
True False There are five mirror planes present in a square. True False There are five proper rotation axes present in a square. True False There is an inversion center in a square. True False A scalene triangle has only the identity operation as a
symmetry element. True False A linear molecule such as CO2 has only one rotation axis that
runs the length of the molecule.
2. Complete the following table by filling in the spaces with the symmetry
elements/operations present in the given chemical species. Do not simply indicate the presence or absence of the element/operation but give detailed information, i.e., if a proper rotation axis is present, the indicate type (C2, C3, etc). If the particular element/operation is not present in the specie, then leave the space empty.
Identity
(E) Proper
Rotation Axes (C)*
Mirror planes
( )
Inversion Center
(i)
Improper Rotation Axes (S)**
SeF2
BHCl2
SiHCl3
[SF5]-
KrF4
SiH2Cl2
SiH3Cl
SiH4
SF6
*Circle the principal axis if more than one rotation axis is present. **Identify only those that are unique in the object, i.e., do not identify improper rotation axes that are coincidental with proper rotation axes.
3. Enter into the smaller box the point group for each of the following species and then list in the larger box the symmetry elements and operations that were instrumental in the determination of the point group (do not list all such things, only the key ones needed to determine the point group. p-dichlorobenzene
Point Group:
Symmetry elements and operations:
m-dichlorobenzene
Point Group:
Symmetry elements and operations:
o-dichlorobenzene
Point Group:
Symmetry elements and operations:
Aluminum containing species shown at bottom of page
Point Group:
Symmetry elements and operations:
Elemental arsenic structure shown at bottom of page (note: all As-As bonds equal in length)
Point Group:
Symmetry elements and operations:
Octahedral Cr compound shown at bottom of page - heavy atom symmetry only (ignore H's)
Point Group: Symmetry elements and operations:
AlC
H
H
H
O As
As
AsAs
NH3
Cr
O
NH3
O
PO
NH3
NH3
boron trifluoride
Point Group:
Symmetry elements and operations:
cyclopropane
Point Group:
Symmetry elements and operations:
propyne
Point Group:
Symmetry elements and operations:
carbon dioxide
Point Group:
Symmetry elements and operations:
iodine pentafluoride
Point Group:
Symmetry elements and operations:
cyclohexane (boat)
Point Group:
Symmetry elements and operations:
hydrogen cyanide Point
Group:
Symmetry elements and operations:
indium trichloride
Point Group:
Symmetry elements and operations:
1,1'-dibromocyclopropane
Point Group:
Symmetry elements and operations:
phenylacetylene
Point Group:
Symmetry elements and operations:
carbon oxysulfide
Point Group:
Symmetry elements and operations:
1-iodonaphthalene Point
Group:
Symmetry elements and operations:
cyclohexane (chair) Point
Group:
Symmetry elements and operations:
PCl4+
Point Group:
Symmetry elements and operations:
cis-1,2-dibromocyclopropane
Point Group:
Symmetry elements and operations:
SiH2Cl2
Point Group:
Symmetry elements and operations:
BeBr2
Point Group:
Symmetry elements and operations:
BrF4
- Point Group:
Symmetry elements and operations:
1,3,5-trichlorobenzene Point
Group:
Symmetry elements and operations:
cumulene (not cumene or isopropylbenzene)
Point Group:
Symmetry elements and operations:
trans-1,2-dibromocyclopropane
Point Group:
Symmetry elements and operations:
oxalate ion (planar configuration)
Point Group:
Symmetry elements and operations:
Cl2
Point Group:
Symmetry elements and operations:
Chrysene
Point Group:
Symmetry elements and operations:
1,2,3-trichlorobenzene Point
Group:
Symmetry elements and operations: