Hydrogen Spectral Lines.ppt
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Bohr Model of the Atom Electrons in Atoms nucleus (+) electron (-) Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Transcript of Hydrogen Spectral Lines.ppt
Bohr Model of the Atom
Electrons in Atoms
nucleus (+)
electron (-)
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Atomic Spectrum
How color tells us about atoms
PrismWhite light is made
up of all the colors of the visible spectrum.
Passing it through a prism separates it.
Author: Thomas V. Green Jr.
If the light is not whiteBy heating a gas or
with electricity we can get it to give off colors.
Passing this light through a prism does something different.
Author: Thomas V. Green Jr.
Atomic SpectrumEach element gives
off its own characteristic colors.
Can be used to identify the atom.
How we know what stars are made of.
Author: Thomas V. Green Jr.
• These are called line spectra
• unique to each element.
• These are emission spectra
• The light is emitted given off.
Author: Thomas V. Green Jr.
Line-Emission Spectrum
ground state
excited state
ENERGY IN PHOTON OUT
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
656 nm486 nm410 nm
434 nm
Wavelength (nm)
PrismSlits
Bohr Model• electrons exist only in orbits with specific
amounts of energy called energy levels• Therefore…• electrons can only gain or lose certain
amounts of energy• only certain photons are produced
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Bohr Model
1
23
456 Energy of photon depends on the difference in energy levels
Bohr’s calculated energies matched the IR, visible, and UV lines for the H atom
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
nucleus
Other ElementsEach element has a unique bright-line
emission spectrum.
i.e. “Atomic Fingerprint”
Helium
Bohr’s calculations only worked for hydrogen!
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Bohr’s Experiment
Kelter, Carr, Scott, Chemistry A Wolrd of Choices 1999, page 76 Animation by Raymond Chang – All rights reserved.
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
(a) Electronic absorption transition
(b) H2 emission spectrum (top), H2
absorption spectrum (bottom)
continuous spectrum
absorption spectrum
emission spectrum
hot source
gasabsorption spectrum
emission spectrum
Hydrogen Spectral Lines
Lyman series(ultraviolet)
Balmer series(visible)
Paschen series(infrared)
Frequency(hertz)
1016 1015 1014
7 6 5 4 3 2 1 n =
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
(ultraviolet)
(visible)
(infrared)
HYDROGEN SPECTRAL LINES
Hydrogen Spectral Lines
A B C D E F Lyman series (UV)
A B C D E Balmer (Visible)
A B C D Paschen (IR)
E1
E2
E3
E4
E5E6
Ener
gy
Bohr’s model of the atom accounted mathematically for the energy of each of the transitions shown.
IRregion
UVregion
656 nm
486 nm
434 nm
410 nm
Davis, Metcalfe, Williams, Castka, Modern Chemistry, 1999, page 97
ionization
Electronic Transitions in the Excited Hydrogen Atom
