Activity 5: The Electronic
Behavior of Atoms
Scientist
Democritus/Dalton
Thomson
Rutherford
Model of the Atom
•Electrons are in fixed
energy levels around
the nucleus
•Energy levels get
closer together as
they get further from
the nucleus.
• Think of a ladder
that isn’t equally
spaced
+
Where are
electrons located?
Energy levels:
•
Regions around the nucleus
where electrons can be found
•Electrons can move from one
energy level to another by
gaining or losing energy
What’s going on here???
crest
trough
Short wavelength
Long wavelength
Wavelength decreases, frequency increases, Energy increases
As you move from Red to Violet light, the
wavelength of the waves decreases.
Long wavelength
Low frequency
LOW ENERGY
Small wavelength
High frequency
High ENERGY
An increase in the frequency of the wave and an increase in
energy of the wave.
• Colors of light are
associated with
energy.
• Red light has the least
energy, while violet
light has the most
energy.
Explain this cartoon…..
• Sunlight reaches Earth's atmosphere
and is scattered in all directions by
all the gases and particles in the air.
Blue light is scattered in all
directions by the tiny molecules of
air in Earth's atmosphere. Blue is
scattered more than other colors
because it travels as shorter,
smaller waves. This is why we see a
blue sky most of the time.
Why not violet?
As the Sun gets lower in the
sky, its light is passing through
more of the atmosphere to
reach you. Even more of the
blue light is scattered, allowing
the reds and yellows to pass
straight through to your eyes.
http://news.discovery.com/videos/why-tell-me-whywhy-is-the-sky-blue.html
Dan Flavin
Flame Test Experiment
• Bohr observed the flame
colors through an
instrument that
separates the light into
its component colors--just like a prism!
Slit
(light enters here)
Grating diffracts light,
separating colors
Light
source
Wavelength
scale
Look in here
This is the spectrum you would observe if you
used a spectroscope to look at a white
computer screen.
How a spectroscope works
ATOMIC EMISSION SPECTRUM
When the flame
colors are
observed through
a spectroscope, a
pattern of bright
lines appears
ATOMIC EMISSION SPECTRUM
The bands of light are called:
ATOMIC EMISSION SPECTRUM
• All elements have a DIFFERENT
pattern of spectral lines that can be
used to identify the element.
• This spectrum is unique to every
element.
Why do we see this?
• Electrons can get
“excited” and move from
lower energy levels to
higher energy levels by
absorbing energy.
• When they fall back down
to a lower energy level the
electron loses energy in
the form of light.
ATOMIC EMISSION SPECTRUM
Atomic Emission
Spectrum
Add
energy
So…
• Electrons start off in the
GROUNDSTATE
• They absorb energy and move
to the EXCITED STATE
• They then lose this absorbed
energy fall back down to the
groundstate and emit light!