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Electrons in Atoms
Electron Configurations
The Nuclear Atom &
Unanswered Questions
• Rutherford
• Model did not show how electrons
occupy space around nucleus.
• Did not answer why electrons are
not pulled into atom’s “+” charged
nucleus.
• Light
• Certain elements emit visible light
when heated into a flame.
• This chemical behavior is related
to the arrangement of the
electrons in its atom.
Wave-like Properties of Light
• Examples include ultraviolet,
infrared light, microwaves, &
radio waves.
• These are known as
Electromagnetic Radiation
Electromagnetic Radiation
• Form of energy that exhibits
wavelike behavior as it travels
through space.
• Moves through a vacuum at a
constant speed of 2.998 x 108 m/s
• Measurable wave properties:
wavelength (λ) and frequency (v)
Quantum Model
• Theory that states that
electrons have wavelike
properties.
• Electrons are thought of waves
confined to the space around
the atomic nucleus. The
frequency of the electrons is
based on the type of element.
Wave
Label amplitude, wavelength, and
frequency.
How has the frequency
& wavelength changed?
How has the frequency &
wavelength changed?
The lower the frequency, the
_________________ the wavelength.
The higher the frequency, the
_________________ the wavelength
Equations:
c= λv
E = hv
E = h c/λ
h=
C=
λ=
V=
Planck’s Constant= 6.626 x 10-34 J*s
speed of light (2.998 x 108 m/s)
wavelength
frequency
Example:
• What is the wavelength of
electromagnetic radiation
having a frequency of 5.00 x
1012 Hz?
Example #2
• What is the frequency of
electromagnetic radiation
having a wavelength of 3.33 x
10-8 m?
Particle Nature of LightThe Quantum Model
• Quantum= minimal amount of
energy required to move an
electron from its present energy
level to the next higher one.
Particle Nature of LightThe Quantum Model
• Quantum Leap= abrupt change
of electrons going from present
energy level to the next higher
one.
• (Think about photosynthesis!!)
Particle Nature of LightThe Quantum Model
• Quantum Mechanical Model (1926)
• Based on math with probability
• Fuzzy cloud of electrons
• Principle Quantum Number (n)
• n = 1 Lowest Energy Level (1s)
• n = 2 Next Higher Energy Level (2s2p)
Sublevels
s
p
d
f
Orbitals
1
3
5
7
Shape
spherical
dumb bell
clover leaf
too hard to visualize
8 x 8 grid
Rules for Electron
Configurations
1.
Aufbau Principle= electrons enter orbitals
of lowest energy first
2.
Pauli Exclusion Principle= 2 electrons in
one orbital must have opposite spins
(directions)
3.
Hund’s Rule= when you have a sublevel
with more than 1 orbital, must have 1
electron in each orbital before you can
double up.
Photoelectric Effect
• Solar powered items (convert light
into electrical energy)
• Photoelectrons
• Wave model does NOT explain this!
• 1905- Einstein stated that
electromagnetic radiation has both
wavelike and particle like natures.
(Stream of bundles of E called
photons)
Reading:
• Read and take notes on your
own on the Atomic Emission
Spectra (p125-126)