1. Chapter 7: Quantum Theory and Atomic Structure
The Nature of Light
Atomic Spectra
The Wave - Particle Duality of Matter and Energy
The Quantum - Mechanical Model of the Atom

2. Chapter 7 - Quantum Theory of the Atom
Read the entire chapter
Answer all the Review Problems.
Problems: 19, 23, 27, 31, 33, 37, 39, 43, 45, 47,
49, 51, 53, 57, 63, 65, 67, 71, 75, 77, 81,

3. What are the electrons doing in the atom?
Why do atoms form ions and molecules?
Why do hydrogen and oxygen “stick” together to
form water?
To understand these questions, we need to understand
the electronic structure of the atom
Electronic structure referes to the way the electrons
are arranged in an atom

4. Atoms are the basic building blocks of matter.
They are the smallest units of an element that can
combine with other elements (that is, take part in
a chemical reaction.

5. Structure of the Atom
The simple view: only three subatomic particles
have a bearing on chemical behavior.
Protons, Neutrons and Electrons

6. Proton is a nuclear particle having a positive charge
equal to that of the electron and a mass
more that 1800 times that of the electrons.
Neutron is a nuclear particle having a mass
almost identical to that of the proton but
with no electric charge
Electron is a negatively charged particle with
the negative charge equal to that of the proton.

7. Protons and neutrons reside together in a
very small volume within the atom
known as the nucleus.
Most of the rest of the atom is space in which
the electrons move

8. electrons
neutrons
protons

9. 1. Each element is composed of extremely small
particles called atoms.
2. All atoms of a given element are identical.
3. Atoms of different elements have different
properties (including different masses).
4. Atoms and elements are not changed into different
types of atoms by chemical reactions.
5. Compounds are formed when atoms of more
than one element combine.

10. We Know:
Atoms (elements) are the basic unit of
chemical stucture and are made of protons, neutrons
and electrons (simplification)
Compounds are made up of elements (atoms) in
difinite proportions. Compounds are also called
Molecules.

11. C 6 12.011 Group Atomic number 14A Atomic symbol Period 2 Atomic mass
(amu)
Parts of the Periodic Table

12. The present theory of the electronic structure of the atom
started with an explanation of the colored light produced
in hot gases and flames
This means we need to know something about the nature
of light and radiant energy
Radiant energy is electromagnetic radiation: light, X rays
All types of radiant energy move through a vacuum at
the speed of light (c) 3.00 x 108 m/s
All radiant energy has wavelike characteristics

13. A wave is periodic in nature and can be characterized
by its wavelength and frequency

14. l l l
l is the distance between any two adjacent identical
points of a wave

15. l
Frequency (n) - the number of wavelengths of that wave
that pass a fixed point in one unit of time (usually 1 sec.)

16. Short wavelength
High Frequency
Long wavelength
low frequency
Wavelength and frequency are related

17. What else do we know?
We said that all types of radiant energy move through
a vacuum at 3.0 x 108 m/s
We know that l is the distance between identical points
on successive waves
We know that n is the number of times per second that
one complete wavelength passes a given point.
So:
c = l n

18. The yellow light given off by a sodium lamp has a
wavelength of 589 nm. What is the frequency of
this radiation?
c = l n
n = c/ l
c = 3.0 x 108 m/s
n = 3.0 x 108 m/s
x 109 nm
= 5.09 x 1014/s
589 nm
1 m

19. Electromagnetic radiation (light) consists of occilations
in electric and magnetic fields that can travel through
space. These occilations can be characterized in terms
of wavelength and frequency
The range of frequencies and wavelengths of
electromagnetic radiation is called the
electromagnetic spectrum
The visible spectrum 400 nm (violet) to 800 nm (red)

21. Fig. 7.3

22. The Spectrum of Electromagnetic Radiation
The wavelength of visible light is between 400 and 700 nanometers
Radio, TV , microwave and infrared radiation have longer wavelengths (shorter frequencies), and lower energies than visible light.
Gamma rays and X-rays have shorter wavelengths (larger frequencies), and higher energies than visible light!

23. Fig. 7.1

24. Fig. 7.2

25. Electromagnetic Radiation
WAVELENGTH - The distance between identical points on successive waves. (  )
FREQUENCY - The number of waves that pass through a particular point per second. ()
AMPLITUDE - The vertical distance from the midline to a peak, or trough in the wave. c 


26. Calculation of Frequency from Wavelength
Problem: The wavelength of an x-ray is 1.00 x10 -9 m or 1 nm, what is
the frequency of this x-ray? If the wavelength of long-wavelength
electromagnetic radiation is 7.65 x 104 m, what is the frequency of this
long-wavelength radiation used to contact submerged nuclear submarines
at sea?
Plan: Use the relationship between wavelength and frequency to obtain
the answer. wavelength x frequency = speed of light!
Solution:
speed of light
wavelength(m)
frequency(cycles/sec) =
3.00 x 108 m/s
1.00 x m a)
frequency = = 3.00 x 1017 cycles/sec
3.00 x 108 m/s
7.65 x 104 m b)
frequency = = x 103 cycles/s

27. Different Behaviors of Waves and Particles
Fig. 7.4

28. The Diffraction Pattern Caused by Light Passing through Two Adjacent Slits
Fig. 7.5

29. The Photoelectric Effect - I
Below the threshold energy, nothing occurs !
Above the threshold, the kinetic energy of the ejected electrons is proportional to the frequency of the light.
Also, when above the threshold, as intensity of the light increases, so does the number of ejected electrons.
All metals experience this effect, but each has a unique threshold frequency.

30. The Photoelectric Effect - II
Albert Einstein
Theorized Photons
Won Nobel prize
Photons have an energy equal to:
E = h
h = Plank’s Constant, and is equal to:
x Jsec

31. Demonstration of the Photoelectric Effect
Fig. 7.7