View
225
Download
0
Category
Tags:
Preview:
Citation preview
•THE BOHR MODEL OF THE ATOM
October 23, 2009
The Bohr Model of Hydrogen Atom
Light absorbed or emitted is from electrons moving between energy levels
Only certain energies are observedTherefore, only certain energy levels exist
Energy levels are Quantized
Energy Adsorption/EmissionEnergy Adsorption/Emission
Absorption and Emission Spectra
Hydrogen Energy Levels
Constant = Rhc = 2.18 x 10-18 JR = Rydberg constant = 1.0974 x 107 m-1
h = Planck’s constant = 6.626 x 10-34 Jsc= velocity of light in vacuum = 3.0 x 108 m/s
En Constant
n2
Each line corresponds to a transition:
Example: n=3 n = 2
En 2.18 x 10-18 J
n2
E photon h hc
€
E3 = −2.18 x 10-18 J
32= −2.42x10−19J
€
E2 = −2.18 x 10-18 J
22= −5.45x10−19J
€
hc
E photon
=(6.626x10−34 J ⋅s)(3.0x108m /s)
−3.03x10−19J= −6.56x10−7m = 656nm
€
E photon = ΔE = E final − E initial = E2 − E3
= −5.45x10−19J − (−2.42x10−19J) = − 3.03x10−19J
Balmer seriesBalmer series
Explanation of line spectra
The emission line with the shortest wavelength is:
1. 12. 23. 34. 45. 5
The emission line with the longest wavelength is:
1. 12. 23. 34. 45. 5
The emission line with the highest energy is:
1. 12. 23. 34. 45. 5
The absorption line with the shortest wavelength is:
1. 12. 23. 34. 45. 5
The absorption line with the lowest energy is:
1. 12. 23. 34. 45. 5
A Revolutionary Idea: Matter Waves
All matter acts as particles and as waves.Macroscopic objects have tiny waves- not observed.
Wave nature only becomes apparent when object is VERY lightFor electrons in atoms, wave properties are important.deBroglie Equation:
h
mv
Matter waves- Examples
Macroscopic object: 200 g rock travelling at 20 m/s has a wavelength:
Electron inside an atom, moving at 40% of the speed of light (0.4 x 3x108m/s):
€
h
m ⋅v=6.626x10−34 J ⋅s
(0.2kg)(20m /s)=1.66x10−34m
€
=h
m ⋅v=
6.626x10−34 J ⋅s
(9.11x10−31kg)(0.4)(3.0x108m /s)= 6.06x10−12m = 0.006nm
Can see matter waves in experiments
Recommended