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Drawing Lewis Structure in Chemical Principles | CH 105, Study notes of Chemistry
Material Type: Notes; Professor: McCormick; Class: Chemical Principles; Subject: Chemistry; University: Northern Michigan University; Term: Winter 2010;
Typology: Study notes
2009/2010
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Announcements
- (^) Quiz 4 is Friday
- (^) Lecture Material (Friday, Monday, & Wednesday)
Drawing Lewis Structures
- Note the number of outer shell electrons contributed by each atom.
- Find the total number of electrons available to form bonds. 3. Attach atoms together using single bonds and deduct the number of electrons used. Central atom is usually written first in the formula
Examples
AlCl 3 CH 2 NH O 3 HCN
Resonance Structures
Sulfur trioxide SO
3 O S O O O S O O O S O O
- (^) a single Lewis structure does not adequately represent the true structure of a molecule
The Nature of Light Low E High E Wavelength ( l ) = distance traveled between successive peaks (nm) Frequency ( n ) = number of waves passing a fixed point in one second (waves/s or 1/s or s
- or Hz).
Electromagnetic Spectrum The various types of radiation seem different to our senses, yet they differ only in their respective l and n. HIGH Energy LOW Energy
--has sufficient energy to cause molecular bonds to
break!
Ultraviolet Radiation
Consider Red Light:
Wavelength = 1.0 x 10
m
Frequency = 3.0 x 10
14
s
Does this correspond to the speed of light?
Light Energy
- (^) both particle-like and wave-like properties
- (^) quantized: energy is not continuous , but consists many individual steps
Photons
- (^) individual bundles of light energy
- (^) do not have mass
- (^) not true particles
- (^) do not have mass
Energy
Wavelength Frequency Energy
long (radiowaves) low low short (X-rays) high high
Energy and wavelength are inversely related
-shorter wavelength means higher energy.
Example Calculations:
E = hn c = ln Find the energy of green light, l =480 nm. Find the energy of microwaves: n = 1.18 x 10 10 s
INPUT Photon of Energy=hv
Quantized Energy
e
-
e
-
Excited State Electron
Quantized Energy
e
-
e
- High Energy Orbit Low Energy Orbit Ground State Energy