Search for notes by fellow students, in your own course and all over the country.
Browse our notes for titles which look like what you need, you can preview any of the notes via a sample of the contents. After you're happy these are the notes you're after simply pop them into your shopping cart.
Title: Molecular Orbital Theory
Description: notes describing molecular orbital theory in chemistry with practice questions
Description: notes describing molecular orbital theory in chemistry with practice questions
Document Preview
Extracts from the notes are below, to see the PDF you'll receive please use the links above
November 13, 2015
Important Information:
Midterm next Wednesday!
PSet#6 due Monday @ 2:30pm
Adaptive Followup for Practice
OH Sunday 36 (Braun Aud)
Lecture 24: MO Theory
Clicker Question #1
Draw the Lewis structure for the molecule CH
CHCH
...
) 8 sigma, 1 pi
b
...
) 9 sigma, 1 pi
d
...
) 8 sigma, 2 pi
solution:
each single bond is a sigma bond, including half of a double bond
...
hybridization must be sp
to form pi bonds because there has to be a
leftover p orbital to make pi bonds
...
a
...
) CO
2
c
...
) NO
e
...
) 0
b
...
) 1
...
5
e
...
2 1 / 2 = ½
why do noble gases not form bonds?
November 13, 2015
● have to put an even amount of electrons in both the antibonding orbitals and the bonding
orbitals → will get a bond order of 0 → there is no net reduction in energy, therefore no
stability is gained by forming a bond
MO’s for 2nd Row Elements
ex: Oxygen bonding to Oxygen
● only look at valence electrons because the core electrons will not contribute to molecular
bonding
2
● valence electrons: 2s 4
2p
○ have one filled 2s orbital (2 electrons) and 3 p orbitals (2p y
2p
and 2p
) (the first
x
z
filled with 2 electrons, and the 2nd and 3rd filled with one electron)
● mix together the two 2s orbitals → will form sigma bonds → get out a σ 2s (bonding)
and σ *2s (antibonding)
● mix together 2p
orbitals (first p orbitals) → form sigma bonds because they will directly
x
overlap in the x plane → form σ 2p
(bonding) and σ *2p
(nonbonding)
x
x
● mix together 2p
orbitals (second p orbitals) → for pi bonds because they will need to
y
interact across a distance since they are parallel to each other → form π 2p
(bonding)
y
and π *2p
(nonbonding)
y
● mix together 2p
orbitals (third p orbitals) → form pi bonds because they will need to
z
interact across a distance since they are parallel to each other in the 3D plane → form π
2p
(bonding) and π *2p
(nonbonding)
z
z
● energetically the π 2p π 2p
and
orbitals are at the same energy → only thing that is
y
z
different is their orientation
● fill all of the lower energy level orbitals (bonding orbitals) in a given energy level first
○ σ 2s → σ *2s → σ 2p σ *2p π 2p π 2p π *2p π *2p
→
→
→
→
→
x
x
y
z
y
z
Clicker Question #4
Which compound is most stable based on MO theory?
a
...
) F
2
2+
c
...
) all equivalent
2+
solution:
fill in order of electron configuration → F will have a bond order of 2
2
Movement Around a Double Bond
● the more electrons between two atoms in a bond, the more restrictive the rotation
○ single > double > triple
● pi bond prevents rotation around bond axis
● light can be used to break the p orbitals and allow rotation
Title: Molecular Orbital Theory
Description: notes describing molecular orbital theory in chemistry with practice questions
Description: notes describing molecular orbital theory in chemistry with practice questions