QUANTUM MECHANICS

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QUANTUM MECHANICS
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MAX PLANCK and the QUANTUM

• electromagnetic energy could be emitted only in
  quantized form
• E hf, where E is energy, h is Planck's constant
  and f is the frequency of the radiation.

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Definition

• Quantum an indivisible entity.
• The magnitude can only take on certain discrete
  numerical values

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• The term photon was coined in 1926 by Gilbert
  Lewis

• The QUANTUM of the electromagnetic field.

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Photons have zero mass and zero electric
charge Photons do carry energy, momentum and
angular momentum
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Photons are produced when one electron moves to
an orbital of less energy And when an unstable
nucleus undergoes nuclear decay And wherever
charged particles are accelerated And atoms
continuously emit photons due to their collisions
with each other
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HYDROGEN LINE SPECTRUM

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Hydrogen Neon Nitrogen Argon
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Electromagnetic Spectrum
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THE WAVE-LIKE ELECTRON
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• Louis Victor de Broglie-French Theoretical
  Physicist
• 1924 doctoral thesis, Recherches sur la théorie
  des quanta (Research on Quantum Theory),
  introduced his theory of electron waves.
• Included the Wave-Particle Duality Theory of
  matter

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• WAVE-PARTICLE DUALITY
• All objects exhibit, at times, a wave-like
  nature, and at other times a particle-like
  nature.
• Photon acts like a PARTICLE
• Photon acts like a WAVE

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• de Broglie suggested that there is a wave
  associated with the moving electron.

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The de Broglie Hypothesis Any moving particle or
object has an associated wavelength
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• Not long after de Broglie showed that the
  electron could be connected with the wave,
  Heisenberg and Schrodinger described the waves
  mathematically.
• Their formulas very closely match the
  experimental observations.

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Heisenberg Uncertainty Principle One cannot
assign, with full precision, values for certain
pairs of observable variables, including momentum
and position, of a single particle at the same
time.
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Schrödinger Wave Equation
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Schrödinger Wave Equation Leads to a series of
mathematical functions called wave functions,
?. ?2 provides information about an electrons
location in an allowable energy state. ?2
probability density
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THE QUANTUM MECHANICAL MODEL OF THE ATOM
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QUANTUM NUMBERS

• Principal Quantum Number (n)
• refers to size and energy of orbital
• Angular Quantum Number (l)
• Distinguishes the shape of the orbitals
• Magnetic Quantum Number (ml)
• distinguishes orientation in space
• Spin Quantum Number (ms)
• gives the 2 possible locations of the spin axis

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The s Orbital
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The p Orbital
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The d Orbitals
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The f Orbitals

• much more complicated in their shape.
• so much so that we are not going to worry about
  them in this course!!!!!

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• The maximum number of electrons that can occupy a
  certain energy level can be calculated from the
  equation 2n2
• Pauli Exclusion Principal an atomic orbital may
  be described at most by two electrons

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• Aufbau Principal electrons must enter orbitals
  of lowest energy first
• Hunds rule when electrons occupy orbitals of
  equal energy, one electron enters each orbital
  until all the orbitals contain one electron with
  spins parallel. Then other electrons enter the
  orbitals with opposite spins.

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Arthur Compton

• The Compton Effect
• When a high energy x-ray photon collides with a
  free electron, it gives some of its energy to
  the electron and a lower energy photon scatters
  off the electron.

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Momentum of a Photon

• the momentum of a photon is the quotient of
  Planks constant and the wavelength of the photon
• P h/?

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References

• http//hyperphysics.phy-astr.gsu.edu/hbase/ems1.ht
  ml
• www.wikipedia.org
• http//theory.uwinnipeg.ca/mod_tech/node154.html
• http//library.thinkquest.org/19662/high/eng/elect
  ron-wave.html
• http//www.chemguide.co.uk/atoms/properties/atomor
  bs.html