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Chapter 7

Chapter 7 The Quantum- Mechanical of the Atom

5 Pages
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Department
Chemistry
Course Code
CHMA10H3
Professor
Shadi Dalili

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Chapter 7 The Quantum- Mechanical of the Atom
7.1 Quantum Mechanics: The Theory That Explains the Behaviour
Quantum-Mechanical Model: A model explaining how electron in atoms and how those
electrons determine the chemical and physical properties in elements
- Classical Physics: At the beginning of the 20th century, matter was described as discrete
particles, electromagnetic radiation were continuous waves, the two were thought to be
separate entities
7.2 The Nature of Light
- Light is electromagnetic radiation (a type of energy embodied by oscillating electric and
magnetic fields)
- Electric and magnetic fields spread as waves through empty space or through a medium, a
wve transmits energy, produced by accelerating electrically charged particles visible light
(electrons) and radio wave (fluctuations of electric current)
- Wavelength/Lambda ( ): Distance between tops of 2 successive crests/troughs, unit in
meters (m), = c/v, 1 nanometer = 10^-9 m
- Amplitude: The maximum height of the wave
- Frequency (v): Number of crests/troughs passing through a given point/unit of time (s-1),
unit: cycle/second
- Velocity (c= speed of light) = 2.9975 x 10^8 m.s-1
-Most humans see between 450 nm (violet) to 700 nm (red)
- Colour of light is determined by wavelength/frequency spectrum (ROYGBV) when
object absorbs some of the white light and reflects other when coloured (THE OBSEVED
COLOUR IS THE COLOUR REFLECTED) white light passing through a prism gives a
continuous spectrum a line spectrum is obtained by applying spark to H2, causing energy
to be released as light (indicates that certain energies are allowed for electron in H=-atom
ENERGY IS QUANTIZED)
- Plancks Postulation: Energy can only be transferred in discrete quantities Delta E =
hv ; v = frequency, h is Plancks constant, 6.626 x 10^-34 Js Energy is not continuous and
is quantized (forced to only have certain discrete values
- Interference: Interaction between waves, 2 types
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1) Constructive Interference: When waves interact to make LARGER wave - waves are in-
phase
2) Destructive Interference: When waves interact so they cancel each other out waves are
out-of-phase
- Diffraction: When travelling waves encounter an obstacle or opening in barriers about the
same size as the , they bend around it
- The diffraction of light through 2 slits separated by distance comparable to results in
interference pattern in diffracted waves characteristic of ALL LIGTH WAVES
- Photoelectric Effects: Heinrich Hertz, 188, observation that many metals emit electrons
when light shine upon it the rate at which electrons leave metals is due to photoelectric
effect would increase if either light of shorter wavelength or higher intensity was used 
Einstein proposed that light energy must come in packet Electromagnetic radiation can
be viewed as a stream of particle-like units called photons/quantum of light
Conclusions:
1)Energy is quantized (hv), 2) Energy of photon depends on v, 3) EM radiation dual
nature both wave and particle
2)ENERGY OF PHOTON: E = hc/
7.3 Atomic Spectroscopy and the Bohr Model
- Neils Bohr proposed that Electron move around the nucleus in only certain allowed
circular orbits Each orbits has a quantum number associated with it , R = Rydbergs
Constant (1.907 x 10^7 m^-1)
7.4 The Wave Nature of Matter: The de Broglie Wavelength, the Uncertainty Principle and
Indeterminacy
- 2 Ideas Leading to New Quantum Mechanics:
1) Wave Particle Duality: Einstein suggested that particle-like properties of light could
explain the photoelectric effect
2) deBroglie, 1924: If light energy has particle-like properties. Doe smatter have wave-like
properties small particles of matter may at times have wavelike properties called
material waves Object = =h/mv/h/p
www.notesolution.com

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Description
Chapter 7 The Quantum- Mechanical of the Atom 7.1 Quantum Mechanics: The Theory That Explains the Behaviour Quantum-Mechanical Model: A model explaining how electron in atoms and how those electrons determine the chemical and physical properties in elements - Classical Physics: At the beginning of the 20 century, matter was described as discrete particles, electromagnetic radiation were continuous waves, the two were thought to be separate entities 7.2 The Nature of Light - Light is electromagnetic radiation (a type of energy embodied by oscillating electric and magnetic fields) - Electric and magnetic fields spread as waves through empty space or through a medium, a wve transmits energy, produced by accelerating electrically charged particles visible light (electrons) and radio wave (fluctuations of electric current) - WavelengthLambda (): Distance between tops of 2 successive creststroughs, unit in meters (m), = cv, 1 nanometer = 10^-9 m - Amplitude: The maximum height of the wave - Frequency (v): Number of creststroughs passing through a given pointunit of time (s-1), unit: cyclesecond - Velocity (c= speed of light) = 2.9975 x 10^8 m.s-1 -Most humans see between 450 nm (violet) to 700 nm (red) - Colour of light is determined by wavelengthfrequency spectrum (ROYGBV) when object absorbs some of the white light and reflects other when coloured (THE OBSEVED COLOUR IS THE COLOUR REFLECTED) white light passing through a prism gives a continuous spectrum a line spectrum is obtained by applying spark to H , c2using energy to be released as light (indicates that certain energies are allowed for electron in H=-atom ENERGY IS QUANTIZED) - Plancks Postulation: Energy can only be transferred in discrete quantities Delta E = hv ; v = frequency, h is Plancks constant, 6.626 x 10^-34 Js Energy is not continuous and is quantized (forced to only have certain discrete values - Interference: Interaction between waves, 2 types www.notesolution.com
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