Chapter 5 UEQ
Electrons in Atoms
What does an atom really look
like?
LEQ
Why is the study of light used to
describe electron
arrangement?
Quantum Mechanics: A view of the atoms
defined in terms of wave behavior and wave
probability.
Transverse wave: wavelength, frequency and
amplitude.
Electromagnetic radiation: energy that travels in
a wave-like pattern and is defined by:
c = λf
Speed of Light: c = λf
c is the symbol for the speed of light.
- this is a constant for all electromagnetic radiation.
- c = 3.0 x 108 m/s
λ is the symbol for the wavelength
- the distance between two equivalent points on a transverse
wave.
- expressed in (m), (cm), or (nm)
f is the symbol for the frequency of a wave.
- this is how often the wave occurs
- expressed in hertz (Hz) meaning cycles per second
Relationship in c = λf
λ and f are inverse to each other: if the
wavelength gets longer, the frequency will get
smaller.
Remember the ‘c’ is a constant for all
electromagnetic radiation. 3.0 x 10 8 m/s
Planck’s Constant
Quantum: the minimum amount of energy that can be
gained or loss by an atom.
Equantum = hf or Equantum = hc
λ
• Planck’s constant 6.626 x 10-34 j-s times the
frequency of the wave is the quantum
energy.
• 1 photon = 1 quantum of energy.
Samplers
1. Orange light has a frequency of 4.8 x 1014 Hz.
What is the energy of one quantum of
orange light?
ans: 3.18 x 10-19 J
2. Which is greater, the energy of one photon of
orange light or the energy from one
quantum of radiation having a wavelength of
3.36 x 10-9 m?
ans: 5.92 x 10-17 J
Sampler
3. A radio station emits radiation at a wavelength of 2.9
m. What is the station frequency in MHz.
ans: 1.03 x 108 /s = 103 MHz
4. What is the wavelength of radiation emitted with a
frequency of 4.3 x 1017 Hz?
ans: 6.98 x 10-10 m
5. At a frequency of 3.44 x 1021 Hz, what is the
wavelength?
ans: 8.7 x 10 -14 m
• The Electromagnetic Spectrum
Gamma
λ 10-14

Light
10-7

(fig 5.5)
Radio
104
f
1022
1014
104
E
10-12
10-19
10-30
Electronmagnetic Spectrum
LEQ
•Why is the Quantum Model of
the atom better than Bohr’s
Model ?
Quantum Mechanic Model
Bohr’s Model:
1. electron occupy defined energy levels
2. electrons occupy from the lowest level to
the highest level.
3. levels are differing distances apart
4. electron will not occupy between the
levels.
Quantum Mechanical Model:
1. electrons occupy regions that are defined
distances from the nucleus
2. those electrons are not found in defined
energy levels
3. electrons are found in areas within a region
of highest probability.
4. electrons are found between the energy
levels. From the lowest region to a higher
region.
LEQ
What are the concepts that
have been developed to give
us a picture of the atom?
Quantum Numbers
Heisenberg Uncertainty Principle: p151
Principle Quantum Numbers (n) are the Energy Levels
Sublevels: s, p, d, and f
Orbital: s = 1, p = 3, d = 5, f = 7
Spin: + and/or – ½
Electron Configuration:
Aufbau Principle: ‘to build’, lowest level to the highest level of
energy.
Pauli’s Exclusion Principle: electrons must spin in opposite
direction to each other.
Hund’s Rule: one in each before fill. One electron MUST occupy
each orbital before another electron enters
Quantum Mechanics
• Electron Configurations
• Valance configurations
• Short hand notation
• Diagonal Rule
• Orbital diagrams
• Orbital Shapes
• Identify elements and/or position of elements based on
configuration.
• 2n2 maximum number of electrons in the principle
quantum number.
• Relative Stability Ground State Configuration
• Valance Electron Dot Configuration
• Diagonal Rule and the Periodic Table
• Shorthand electron configuration