1. The Electronic Structure of Atoms
Ch. 7

2. Properties of Waves
Wavelength (λ) is the distance between identical points on successive waves.
Amplitude is the vertical distance from the midline of a wave to the peak or trough.
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3. The speed (u) of the wave = λ x ν
Properties of Waves
Frequency (v) is the number of waves that pass through a particular point in 1 second (Hz = 1 cycle/s).
The speed (u) of the wave = λ x ν
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4. Speed of light (c) in vacuum = 3.00 x 108 m/s
Maxwell (1873), proposed that visible light consists of electromagnetic waves.
Electromagnetic radiation is the emission and transmission of energy in the form of electromagnetic waves.
Speed of light (c) in vacuum = 3.00 x 108 m/s
All electromagnetic radiation
λ x ν = c
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5. Example 7.1
The wavelength of green light from a traffic signal is centered at 522 nm. What is the frequency of this radiation?
Remembering that 3x108 m/s = 3x1017 nm/s will make your life easier!
5.75 x 1014 s-1
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7. l x n = c l = c/n l = 3.00 x 108 m/s / 6.0 x 104 Hz l = 5.0 x 103 m
A photon has a frequency of 6.0 x 104 Hz. Convert
this frequency into wavelength (nm). Does this
frequency fall in the visible region? l n
l x n = c
l = c/n
l = 3.00 x 108 m/s / 6.0 x 104 Hz
l = 5.0 x 103 m
l = 5.0 x 1012 nm
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8. Photon is a “particle” of light
Energy (light) is emitted or absorbed in discrete units (quantum).
E = h x n
Planck’s constant (h)
h = 6.63 x J•s
Light has both:
wave nature
particle nature
Early evidence for particle-like behaviour (or quantization). The only equation that could correctly predict the intensity of radiation emitted by a black body at both long and short wavelengths included a term for quantized energy (b/c Planck proposed that electrons could only oscillate at certain frequencies).
Photon is a “particle” of light
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9. E = 6.63 x 10-34 (J•s) x 3.00 x 10 8 (m/s) / 0.154 x 10-9 (m)
When copper is bombarded with high-energy photons, X rays are emitted. Calculate the energy (in joules) associated with the photons if the wavelength of the X rays is nm.
E = h x n
E = h x c / l
E = 6.63 x (J•s) x 3.00 x 10 8 (m/s) / x 10-9 (m)
E = 1.29 x J
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10. Line Emission Spectrum of Hydrogen Atoms
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12. Electrocution of a pickle
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13. …and fireworks
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14. Sodium Chloride (NaCl) yellow / orange
lithium
sodium
potassium
SALT
COLOR OF FLAME
Sodium Chloride (NaCl)
yellow / orange
Copper (II) Chloride (CuCl22)
green
Lithium Chloride (LiCl)
fuschia
Calcium Chloride (CaCl2)
orange
Strontium Chloride (SrCl2)
red
Barium Chloride (BaCl2)
yellow / green
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15. n (principal quantum number) = 1,2,3,…
Bohr’s model of the atom (1913)
e- can only have specific (quantized) energy values
light is emitted as e- moves from one energy level to a lower energy level
En = -RH
( ) 1 n2
n (principal quantum number) = 1,2,3,…
RH (Rydberg constant) = 2.18 x 10-18J
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16. E = hn
E = hn
Stopped here
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