quantum physics quantum the smallest quantity of a substance that still has the specific...
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Quantum PhysicsQuantum Physics Quantum
The smallest quantity of a substance that still has the specific properties of that substance
• Discrete vs. Continuous
Albert Einstein showed that light is quantized and contains photons
• Packets of energy
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Quantum PhysicsQuantum Physics Balmer Series
How did physicists determine that the energy levels of electrons are quantized?
• Isaac Newton – prism and sunlight → light is a wave
• Interference patterns like with water → light is a wave
• Joseph von Fraunhofer – the Sun’s spectrum has gaps → ?
• Observations of gas emission and absorption spectrum → ?
J. J. Balmer develops an equation that analyzes the pattern on the spectral lines that are observed.
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Quantum PhysicsQuantum Physics
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Quantum PhysicsQuantum Physics Photons
Max Planck showed how the radiation emitted or absorbed by an object was quantized but still thought of light as a wave.
• Einstein showed that photons have energy E = hf
• Confirmed though experimentation by Robert Millikan
Since h = 6.63 x 10-34 Js, each photon carries a very small amount of energy
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Quantum PhysicsQuantum Physics Photoelectric Effect
Shining light on metal could cause electrons to be ejected from the metal.
• This could not be explained using the wave theory of light
Einstein’s photon theory of light explained the observations concerning the ejection of electrons from metals.
• Waves vs. Photons
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Quantum PhysicsQuantum Physics The Bohr atom
Thomson, Rutherford and Millikan discover the structure of the atom
Classical EM theory could not explain this structure
Niels Bohr developed a model of the atom where the electrons had certain stable states that had quantized radii and energy
• Bound states of the electron in hydrogen
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Quantum PhysicsQuantum Physics Energy levels, photons and spectral lines
Bohr’s model of the atom matches the observations of spectral lines from hydrogen
• “Jumping” of the electron between energy levels
Einstein and Planck explained how a photon is emitted or absorbed by an atom
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Quantum PhysicsQuantum Physics Energy levels, photons and spectral lines
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Quantum PhysicsQuantum Physics Energy levels, photons and spectral lines
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Quantum PhysicsQuantum Physics Energy levels, photons and spectral lines
Louis de Broglie showed that electrons are standing waves that have mass and charge
• They overlap the Bohr “orbits”
• Explains why electron energy levels are quantized and why electrons do not spiral into the positive nucleus
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Quantum PhysicsQuantum Physics Energy levels, photons and spectral lines
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Quantum PhysicsQuantum Physics Elements
Many substances but few “building blocks”
• Think of the number of words and letters in English
The Periodic Table• Tells us about the structure of elements and
how they behave
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Quantum PhysicsQuantum Physics Elements
Metals, nonmetals and metalloids• Hydrogen is different than the others
Most elements are found in combination with other elements
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