Transcript Electrons can be in different orbits of certain energies

Outcome
• Investigate and observe the
colors of the light emitted by
various elements and study
their atomic spectrum.
Based on Bohr’s model
Electrons can be in different orbits of
certain energies, called energy levels.
To change its
energy levels,
an electron
must either
absorb or emit
energy.
An Excited Atom
Energy
Excited atom
Photon of
red light
emitted
atom in
lower energy state
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 326
Atomic spectra
• When elements are heated to
higher temperatures, some of
the electrons are excited to
higher energy levels. When
these excited electrons fall
back to lower energy levels,
they release excess energy as
visible light called photons
How do fire works
produce their brilliant
colors?
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Flame Test for Cations
lithium
Prep Chemistry
sodium
potassium
Schrempp/Haus
copper
Atomic Structure
8
16.11
The Flame Test
• The color of the emitted light
depends on its energy. Blue light is
more energetic than red light. The
characteristic color of the light
produced when substances are
heated are the basis of the flame
test.
The photons with the highest
energy correspond to the
shortest wavelengths.
Longer Wavelength, Lower Energy
Prep Chemistry
Schrempp/Haus
Atomic Structure
10
Electron transitions
involve jumps of
definite amounts of
energy (quanta).
This produces bands
of light with definite
wavelengths.
Prep Chemistry
Schrempp/Haus
Atomic Structure
11
Types of electromagnetic radiation:
Prep Chemistry
Schrempp/Haus
Atomic Structure
12
The Electromagnetic
Spectrum
L
O
W
Increasing frequency
Increasing photon energy
AM radio
E
N
E
R
G
Y
H
I
G
H
Decreasing wavelength
V
i
s
i
b
l
e
Television
channels
FM
Short wave
radio
radio
Radar
Microwave
Radio Waves
infrared
R
Red
O
Orange
Y
G
Yellow
Green
L
i
g
h
t
UV
Rays
Gamma Rays
X- Rays
B
Blue
I
Indigo
V
Violet
E
N
E
R
G
Y
Long
Wavelength
=
Low Frequency
=
Low ENERGY
Wavelength Table
Short
Wavelength
=
High Frequency
=
High ENERGY
Prep Chemistry
Schrempp/Haus
Atomic Structure
14
• Speed of light = frequency of
light x wavelength of light
Longer Wavelength
Higher Frequency and Energy
Prep Chemistry
Schrempp/Haus
Atomic Structure
16