The document discusses light and atomic structure. It explains that electrons can only occupy certain energy levels within an atom and will absorb or emit photons of light of specific wavelengths as they move between these levels. The document also introduces the Bohr model of the hydrogen atom and how electrons transitioning between energy levels leads to emission spectra that are unique for each element.

1. Teacher Prep
• Spectroscope
• Gas tubes

2. Revisiting Atomic Structure
What you know isn’t necessarily what it is.

3. LIGHT AND ATOMIC
STRUCTURE

4. LIGHT AND ATOMIC STRUCTURE
Spectroscope Activity
What do you see?
What do you think it means?
What is the source of what you observe?

5. LIGHT AND ATOMIC STRUCTURE
Light & Atomic Structure
Visible light consists of electromagnetic (EM) waves
which our retina can detect and our brain can
interpret.

6. LIGHT AND ATOMIC STRUCTURE
Light & Atomic Structure
In a vacuum, all EM waves travel at the speed of
light.
c=lxf
c = speed of light = 3.00 x 108 m/s
l = wavelength in meters
f = frequency in Hertz (Hz = s-1)

7. LIGHT AND ATOMIC STRUCTURE
Light & Atomic Structure
Each shade of colour is a result of a very specific
wavelength of light.
410 nm 434 nm 486 nm 656 nm

8. LIGHT AND ATOMIC STRUCTURE
Light & Atomic Structure
Why do these lines appear?
The electrons of atoms prefer to remain at the
lowest energy level.
Draw the Bohr-Rutherford diagram of H.
H
What happens to the electron when it absorbs
energy?

9. LIGHT AND ATOMIC STRUCTURE
Light & Atomic Structure
What happens to the electron when it absorbs
energy?
ENERGY
ENERGY
H
Electrons move to higher energy levels when excited.
Electrons drop to a lower energy level and release energy.

10. LIGHT AND ATOMIC STRUCTURE
Light & Atomic Structure
Light in the visible spectrum
is only observed when
electrons drop from a
specific high range of
energy levels to a
specific low range of
energy levels.
Due to different electron
configurations, each
element has a different
emission spectrum.

11. LIGHT AND ATOMIC STRUCTURE
Light & Atomic Structure

12. LIGHT AND ATOMIC STRUCTURE
Light & Atomic Structure
Atoms will only absorb specific amounts of energy
(photon). Electrons must always be located at a
defined energy level, not in between.
E=hxf OR E=hxn
E = energy in Joules
h = Planck’s constant = 6.6262 x 10-34 J•s
f (n)= frequency in Hertz (Hz = s-1)

13. LIGHT AND ATOMIC STRUCTURE
Summary
Another symbol for frequency

14. LIGHT AND ATOMIC STRUCTURE
The “Ground State” is the lowest energy level available to the
electron. Other energy levels may be added as follows:
Ground state
ELECTRON
Energy levels E1 NUCLEUS
continue to E
E3 2
get closer E4
until they E5
finally
converge at . . . . . E∞
THE HYDROGEN ATOM

15. LIGHT AND ATOMIC STRUCTURE
Frequency/ 1015 Hz
EMISSION
LINE
SPECTRUM
2.4 2.6 2.8 3.0 3.2
As the electron falls
from higher to lower 1
energy level, E2 to E1,
a photon of light is 2
emitted with
3
frequency, f, given by 4
the equation E = h x f 5

16. LIGHT AND ATOMIC STRUCTURE
Frequency/ 1015 Hz
EMISSION
LINE
SPECTRUM
2.4 2.6 2.8 3.0 3.2

17. LIGHT AND ATOMIC STRUCTURE
Frequency/ 1015 Hz
EMISSION
LINE
SPECTRUM
2.4 2.6 2.8 3.0 3.2

18. LIGHT AND ATOMIC STRUCTURE
Frequency/ 1015 Hz
EMISSION
LINE
SPECTRUM
2.4 2.6 2.8 3.0 3.2