covalent bonding: orbitals b. copyright © houghton mifflin company. all rights reserved. 14a–2...
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Covalent Bonding: Orbitals
b
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Figure 13.1: (a) The interaction of two hydrogen atoms (b) Energy profile as a function of the distance
between the nuclei of the hydrogen atoms.
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Figure 13.1: (a) The interaction of two hydrogen atoms (b) Energy profile as a function of the distance
between the nuclei of the hydrogen atoms.
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Figure 14.25: The combination of hydrogen 1s atomic orbitals to form MOs
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Auto mufflers use destructive interferenceof sound waves to reduce engine noises.
(- sign flips phase of the sound wave function)
- = 0
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Bose is $200. Want todo it yourself?See Web site.
http://www.headwize.com/projects/noise_prj.htm
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Amplitudes of wave functions added
An analogy between light waves and atomic wave functions.
Amplitudes of wave functions subtracted.
NOTE: +/- signs show PHASES of waves, NOTCHARGES!
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Figure 14.26: (a) The MO energy-level diagram for the H2 molecule (b) The shapes of the Mos are obtained
by squaring the wave functions for MO1 and MO2.
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Figure 14.27: Bonding and anitbonding MOs
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Figure 14.28: MO energy-level diagram for the H2 molecule
# BONDING e’s = 2
# ANTIBONDING e’s = 0
Bond order = ½(2-0) = 1
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Figure 14.29: The MO energy-level diagram for the He2 molecule
# BONDING e’s = 2
# ANTIBONDING e’s = 2
Bond order = ½(2-2) = 0
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Figure 14.29: The MO energy-level diagram for the He2 molecule
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Figure 14.30: The MO energy-level diagram for the He2
+ ion.
# BONDING e’s = 2
# ANTIBONDING e’s = 1
Bond order = ½(2-1) = ½
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Figure 14.31: The MO energy-level diagram for the H2
+ ion
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Figure 14.32: The MO energy-level diagram for the H2
- ion
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Figure 14.33: The relative sizes of the lithium 1s and 2s atomic orbitals
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Figure 14.34: The MO energy-level diagram for the Li2 molecule
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Figure 14.35: The three mutually perpendicular 2p orbitals on two adjacent boron atoms.
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Figure 14.37: The expected MO energy-level diagram for the combustion of the 2P orbitals
on two boron atoms.
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Figure 14.36: The two p oribitals on the boron atom that overlap head-on combine to form
bonding and antibonding orbitals.
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Figure 14.36: The two p oribitals on the boron atom that overlap head-on combine to form
bonding and antibonding orbitals.
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Figure 14.37: The expected MO energy-level diagram for the combustion of the 2P orbitals
on two boron atoms.
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Figure 14.37: The expected MO energy-level diagram for the combustion of the 2P orbitals
on two boron atoms.
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Figure 14.37: The expected MO energy-level diagram for the combustion of the 2P orbitals
on two boron atoms.
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Figure 14.38: The expected MO energy-level diagram for the B2 molecule
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Figure 14.40: The correct MO energy-level diagram for the B2 molecule.
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Figure 14.39: An apparatus used to measure the paramagnetism of a sample
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Figure 14.41: The MO energy-level diagrams, bond orders, bond energies, and bond lengths for the
diatomic molecules, B2 through F2.
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Figure 14.42: When liquid oxygen is poured into the space between the poles of a strong magnet, it remains
there until it boils away.
Source: Donald Clegg
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Figure 14.43: The MO energy-level diagram for the NO molecule
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Figure 14.44: The MO energy-level diagram for both the NO+ and CN- ions
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Figure 14.45: A partial MO energy-level diagram for the HF molecule
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Figure 14.46: The electron probability distribution in the bonding MO of the HF molecule
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Spectroscopy
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Electromagnetic spectrum
(wavelength) x (frequency) = speed [m/s]
λν = c [108 m/s]
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Electromagnetic spectrum
λν
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WHAT MAKES A MOLECULE ABSORB LIGHT?
When should you push?
AT THE RESONANTFREQUENCY
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λν=cAT THE RESONANTFREQUENCY
14* Electronic transitions: ~ 6 x 10 sec.
500 nm (UV-VIS)
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Figure 14.55: The molecular orbital diagram for the ground state of NO+
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λν=cAT THE RESONANTFREQUENCY
1
13
4
* Nuclear vibration: ~ 3 x
* E
10 sec
lectronic transitions: ~ 6 x 10 se
.
10,000 nm (
* molecula
c.
5
r rotat
00 nm (UV-VIS
ion:
mi
IR)
crowaves
)
VIBRATING
DIPOLES!
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What makes a molecule absorb light?
[cm-1] = 1/λ = ν/c =E/hc
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Figure 14.60: The three fundamental vibrations for sulfur dioxide
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What makes a molecule absorb light?
3200 cm−1 broad, strong O-H stretch (alcohols) 3000 cm−1 broad, medium O-H stretch (carboxylic acids) 1200 cm−1 strong, O-H bending 2800 cm−1 strong, C-H stretch 1400 cm−1 variable, C-H bending 1700 cm−1 strong, C=O stretch 1200 cm−1 strong, C-O stretch
What makes a molecule absorb light?
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Figure 14.61: The infrared spectrum of CH2Cl2.
What makes a molecule absorb light?
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Figure 14.52: Schematic representation of two electronic energy levels in a molecule
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Figure 14.53: The various types of transitions are shown by vertical arrows.
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Figure 14.54: Spectrum corresponding to the changes indicated in Fig. 14.53.
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The molecular structure of beta-carotene
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Figure 14.57: The electronic absorption spectrum of beta-carotene.
VIBRATIONS
VIBRATIONS
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Figure 14.58: The potential curve for a diatomic molecule
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Figure 14.59: Morse energy curve for a diatomic molecule.
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Figure 14.62: Representations of the two spin states of the proton interacting
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Figure 14.63: The molecular structure of bromoethane
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Figure 14.64: The expected NMR spectrum for bromoethane
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Figure 14.65: The spin of proton Hy can by "up" or "down"
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Figure 14.66: The spins for protons Hy can be "up", can be opposed (in 2 ways) or can both be "down"
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Figure 14.67: The spins for the protons Hy can by arranged as shown in (a) leading to four different magnetic environments
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Figure 14.68: The NMR spectrum of CH3CH2Br (bromoethane) with TMS reference
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Figure 14.69: The molecule (2-butanone)
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Figure 14.70: A technician speaks to a patient before heis moved intot eh cavity of a magnetic
resonance imaging (MRI) machine.
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Figure 14.71: A colored Magnetic Resonance Imaging (MRI) scan through a human head,
showing a healthy brain in side view.