Notes: Activity 5 - The Electronic Behavior of Atoms

The Electromagnetic
Spectrum, Spectroscopy,
and Atomic Structure

Electromagnetic Spectrum
• The whole range of electromagne0c radia0on
• Includes the following
• Radio waves
• Microwaves
• Infrared Waves
• Visible Light
• Ultraviolet Waves
• X-­‐rays
• Gamma Rays
• The only difference between them is the amount of energy they
contain

Visible Light
• In 1665 Isaac Newton discovered that white light
was composed of all the colors in the rainbow.
• Used a prism to separate white light into individual colors
• Makes up a very narrow por0on of the
electromagne0c spectrum
• Different colors carry a different amount of energy

• Our eyes & brain interpret
different amounts of
energy as different colors
• Violet has the most amount
of energy
• Red has the least amount of
energy

Continuous Spectrum
• A parade of all the colors
are in visible light
• Can be produced by a
hea0ng a solid, a liquid or
an opaque gas to a fairly
high temperature
(several thousand
degrees Fahrenheit)
• Example: rainbow

Emission Spectrum
• The spectrum of light released from excited atoms
of an element
• The light emiWed by an element separates into
discrete lines
• Each element produces its own unique set of lines
• Can be used to iden0fy an element

How is an emission line spectrum
created?
• According to Bohr’s Model
of the atom, electrons on
an energy level contain a
certain amount of energy
• These electrons can only
move between energy
levels by gaining or losing
an exact amount of energy
• This is known as a Quantum of
Energy

Quantized Energy
• Quan0zed energy is like
a staircase
• It takes a certain amount
of energy to go up and
down the stairs
• Con0nuous energy is like
a ramp
• Any amount of energy can
be used to go up and down
the ramp

• When electrons absorb
energy, they only need a
quantum of energy to to
move to a higher energy
level
• Electrons cannot stay in
this new energy level, so
they fall back to a lower
energy level
• When they fall back, they
release (emit) this energy in
the form of light
• Emit only certain amounts of
energy, resul0ng in specific
colors of light

• Each element has its own unique Bohr model with
different energy spacing between each level
• So each atom produces its own set of unique colors

• hWp://
www.bbc.co.uk/
schools/gcsebitesize/
science/edexcel/
electromagne0c_spe
ctrum/
electromagne0cspect
rumact.shtml
• hWp://video.pbs.org/
video/2219781967/
• hWp://
www.schooltube.co
m/video/
6ea0d020a582f8d6b
1c1/The-­‐
Electromagne0c-­‐
Spectrum

TYPES OF VISIBLE SPECTRA

EMISSION SPECTRUM
• A range of frequencies of electromagne0c
radia0on emiWed by an atom s0mulated by either
heat or electricity

EMISSION SPECTRUM
• Bohr aWempted to explain emission spectra

BOHR MODEL
• Electrons orbit nucleus in
specific, fixed orbits called
energy levels.
• Each atom has certain,
allowed orbits which
correspond to certain
allowed energies.

EMISSION SPECTRUM
• hWp://www.youtube.com/watch?v=QI50GBUJ48s

EMISSION SPECTRA:
EXPLAINED
1. An electron in its ground state ABSORBS a
quantum of energy and moves to an excited
state
• Ground state – lowest energy state
• Excited state – higher energy state
• Quantum – a discrete or particular amount

2. The electron falls back to the ground state and
RELEASES energy in the form of light.

EMISSION SPECTRA
• hWp://www.youtube.com/watch?v=8TJ2GlWSPxI

EMISSION SPECTRUM:
QUESTIONS
1. Where was the ground state?
2. Where were the excited states?
3. What energy level did the electron move to
when it absorbed red light?
4. Why did it fall back to its ground state from the
excited state?
5. What energy level did the electron move to
when it absorbed purple light?
6. Compare and explain the observed transi0ons.

IN SUMMARY