CEM 411: Advanced Inorganic Chemistry - Exam 1

154 pm

134 pm

141 pm

1. cyclic
2. planar
3. (4n+2) pi electrons
4. conjugated

1. cyclic
2. planar
3. (4n) pi electrons
4. conjugated

Fails any of the following criteria:
1. cyclic
2. planar
3. 4n+2 pi electrons / 4n pi electrons
4. conjugated

120 degrees

<120 degrees

109.5 degrees

4

Same number of protons but different number of neutrons

Releases a helium nucleus

Releases an electron

Releases a photon

1. nuclear decay
2. transmutation

1. alpha (helium nucleus)
2. beta (electron)
3. positron (positive electron)
4. gamma (photon)

1. alpha ray
2. beta ray
3. gamma ray

A movement (reflection

1. reflection (sigma)
2. proper rotation (Cn)
3. improper rotation (Sn)
4. inversion (i)
5. identity (E)

Do nothing

A counter-clockwise rotation of 360/n about an axis

Internal reflection through a plane of symmetry

1. sigma h: perpendicular to the principal axis
2. sigma v: parallel to the principal axis
3. sigma d: (dihedral) parallel to the principal axis

Each atom is moved along a straight line through the center of the object (inversion center) to a point an equal distance

A rotation of 360/n followed by a perpendicular reflection

These point groups only contain one or two symmetry operations

1. C1: identity
2. Cs: identity and sigma h
3. Ci: identity and inversion

1. Td: no inversion center
2. Oh
3. Ih

Have a C infinity axis as the principal rotation axis

1. C infinity v
2. D infinity h

Have nC2 axes perpendicular to a principle axis (Cn)

1. Dn
2. Dnh
3. Dnd

Have a principal axis but no perpendicular C2 axes

1. Cn
2. Cnv
3. Cnh

If an object has a principal axis and an S2n axis but no perpendicular C2 axes and no mirror planes

A reducible representation (the sum of the numbers across the diagonal of each matrix)

The sum of symmetry operations of a point group

Symmetric to principal axis

Antisymmetric to principal axis

Character under identity will be 2

Character under identity will be 3

Symmetric to inversion

Antisymmetric to inversion

Symmetric to the next operation class after the principal axis

Antisymmetric to the next operation class after the principal axis

List of the complete set of irreductible representations and symmetry classes of a point group

Irreductible representations

Symmetry classes

discovered negatively charged particles (e-) in the cathode ray by having the "light" bend when touched by a magnet

Discovered the nucleus by deflecting alpha particles through gold foil: some did not go through but instead bounced off the nucleus of the gold atom

determined the charge of the electron

The amount of energy required to remove an electron from an atom

increases diagonally left to right

The emission of electrons from a metal when light shines on the metal

energy measurement of electrons emitted from solids

The amount of energy released when an electron is attached to a neutral atom to form a negative ion

increases diagonally left to right

Determined energy was in quanta (small packets)

(bonding electrons - antibonding electrons)/2

Possible by an end-to-end overlap of two orbitals

1. two s orbitals overlap
2. one s orbital and one p orbital overlap
3. two p orbitals overlap

Constructive interference for side-to-side overlap of two p orbitals

created by a linear combination of atomic orbitals

120.3 pm

a geometric object (plane

3N-6

All atoms move the same amount in the same direction the molecule moves

0

1

-1

x

Rx

The representations that remain after translation and rotation is determined

Vibration must change the dipole moment: only irreducible representations with x

Must change the polarizability: only irreducible representations that transform like the binary products of x

1/order*(sum of: # of operations in the class*character of reducible representation*character of irreducible representation)

two electrons in one molecular orbital

four electrons

six electrons

There are 1 sigma and 2 pi bonds: uses 2sp hybridized orbitals to make the sigma bond leaving 2 p orbitals to make the 2 pi bonds.