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CHEM 1320 Study Guide - Hmu Language, Diamagnetism, Fluorine

15 pages42 viewsFall 2013

Department
Chemistry
Course Code
CHEM 1320
Professor
Ganley

Page:
of 15
Chapter 7: Quantum Theory and the Electronic Structure of
Atoms
10/11
Wavelength ( ): peak-to-peak distance on successive wavesλ
Amplitude: vertical distance from midline to peak
Frequency ( ): # of waves pass through a point in 1 sec. ν
(Hz=1cycle/s)
Speed ( ) of the wave: X υ λ ν
Higher the frequency, shorter the wavelength
Lower the frequency, longer the wavelength
Inverse relationship
Maxwell (1873): visible light is electromagnetic (EM) waves.
EM radiation: emission & transmission of energy in the form of
electromagnetic waves.
Speed of light (c)= 3.00 X 10^8m/s
ALL EM radiation: λX ν=c
Violent=shortest wavelength, longest frequency
Red=longest wavelength, shortest frequency
Frequency:
Units of frequency:
Sec^-1 S^-1 Cycles per second (cps) Hz (Hertz)
Symbol: (ν) (Greek nu)
Wavelength:
Unit: (λ)
Different λ=different kind of light
Measured in nm (one billionth of a meter)
250nm=250 X 10^-9m
Frequency Wavelength
Can convert λ and frequency (ν):
In meters  λ=c/ν c=3.00 X 10^8m/s
A radio station is 103.5 FM. What wavelength does it broadcast?
103.5FM=103.5MHz=103.5 million s^-1
λ=3.00 X 10^8 m/s
---------------------- = 2.8 m (~10ft)
103,500,000s^-1
What is the frequency of light if its wavelength is 200 m?
=νc/λ
=3.00 X 10^8 m/s
---------------------- = 1,500,000s^-1 1.5 X 10^6s^-1
200m
Visible=most intense
Wavelength=most abundant
UV=most damaging
Mystery #1
“Heated Solids Problem”
-Heated solids emit EM radiation over a wide range of
wavelengths.
White-hot object: hotter than red-hot
Different wavelengths  different amounts of energy
Energy (light) is emitted or absorbed in discrete units (quantum).
E=h X ν
Planck’s constant (h)
h=6.63 X 10^-34 Js
What is the energy of UV light with a frequency of
1.00 X 10^15 s^-1?
E=hν=(6.63 X 10^-34 Js)(1 X 10^15 s^-1)
E=6.63 X 10^-18 J
E=hν=hc/λ Since ν=c/λ
Compare to a radio wave of λ 3 X 10^9 m
E= hc/λ =(6.63 X 10^-34 Js)(3.00 X 10^8 m/s)
-------------------------------------------------
3 X 10^9 m
E=6.63 X 10^-35J
What happens when light hits matter?
IR-molecules vibrate, matter heats up

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