Transcript Niels Bohr’s Energy Levels

Niels Bohr’s Energy Levels
• Electrons in certain energy levels
– Orbits with certain amounts of
energy
• Low energy levels: closer to nucleus
• High energy levels: farther from
nucleus
• Ground state
– Electrons in lowest energy level
possible
• Aufbau principle
– Electrons will occupy the lowest available
energy level
Episode 303
Excited Atom
• Atom has absorbed energy
– Quanta – Energy required to excite an
electron
• Excited state is unstable
• Atom soon emits same amount of absorbed
energy
• Energy seen as visible light
– Photon – particle with no mass containing a
quanta of energy
– COLOR
Episode 303
Wave Description of Light
• Wavelength (λ)
– Distance between corresponding points on
adjacent waves
• Frequency(f or γ)
– The number of waves passing a given point in a
given time
– Hertz
• C = λf
– C = 3.0 x 108 m/s : speed of light
Episode 303
Electromagnetic Spectrum
http://education.jlab.org/frost/speed_of_light.html
• What is the frequency of
light if the wavelength is
6.0 x 10-7 m?
C = λf
C = 3.0 x 108 m/s : speed of light
3.0 x 108 m/s = (6.0 x10-7 m) f
3.0 x 108 m/s
=f
-7
6.0 x10 m
5.0 x 1014/s = f
Episode 303
Electromagnetic Spectrum
• What is the wavelength
of light if its frequency
is 5.0 x 1014 Hertz?
C = λf
C = 3.0 x 108 m/s : speed of light
3.0 x 108 m/s = λ(5.0 x 1014/s)
3.0 x 108 m/s
=λ
14
5.0 x 10 /s
6.0 x 10-7 m = λ
Episode 303
Particle Description of Light
• Energy exists as particles called
quanta
– Photoelectric Effect
• Metal emits electrons when light strikes the
metal
• E =hf
– h is Plank’s Constant
– 6.626 x 10-34 Js
Episode 303
Electromagnetic Spectrum
• How much energy does
light contain if its
frequency is 5.0 x 1014
Hertz?
E = hf
h = 6.626 x 10-34 Js : Plank’s Constant
E= (6.626 x 10-34Js)(5.0 x 1014/s)
E = 3.3 x 10-19 J
Episode 303
The Modern View of Light
• Light has a dual nature
– Light may behave as a wave
– Light may behave as a stream of particles
called quanta or photons
Episode 303
Spectroscopy
• Spectral lines
represent energy
released as
electrons return to
lower energy levels
• Spectral lines
identify an element
• Called the Bright
Line Spectrum of
an Element
Episode 303
Orbital
http://www.youtube.com/watch?v=rNM21emkMJo&feature=related
• Region of space where an electron is
likely to be found
– Heisenberg Uncertainty Principle
• Impossible to determine location and velocity
of a particle
Episode 303