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Wave-Particle Duality:The Beginnings of Quantum Mechanics
• Explain the basics of wave-particle duality.
• Define the relationship between quantum, photon and electron.
• Describe how a produced line spectra relates to the Bohr diagram for a specific element.
Additional KEY Terms
Absorption Spectra
PHOTOELECTRIC EFFECT
Shining light on a metal surface will immediately eject electrons.
Electrons given enough energy (ionization) can escape the attraction of the nucleus.
*Light is acting like a “particle” in this experiment – collision.
Einstein (1905) - electromagnetic radiation is a stream of tiny bundles of energy called photons.
Photons have no mass but carry a quantum of energy.
One photon can remove one electron.
Light is an electromagnetic wave, yet it contains particle-like photons of energy.
Only high frequency light (> 1.14 x 10 15 Hz) will eject electrons - acting as particle.
Can only explain it if you think of it using photons in a collision.
Only more intense light (higher amplitude) will eject more electrons - acting as wave.
Can only explain it if you think of it as changing the amplitude of the wave.
Compton (1922) – first experiment to show particle and wave properties of EMR simultaneously.
Incoming x-rays lost energy and scattered in a way that can be explained with physics of collisions.
Quantum Mechanical Model of the Atom
Bohr (1922) – explained unique line spectrums by restricting electrons to fixed orbits with different quantized energy levels.
1. Electron absorbs radiation and jumps fromground state (its resting state) to a higher unstable energy level (excited state).
2. Electron soon loses energy and drops back down to a lower energy level – emitting the absorbed EMR.
• Levels are discrete like quanta – no in between.
• Each jump/drop is associated with a specific frequency photon - same transition, same photon.
The size of nucleus will affect electron position around the atom.
Cl:
17 e-
Na:11 p+
11 e- 17 p+
*Each element has a unique line spectrum as each element has a unique atomic configuration.
Absorption spectrum – portion of visible light absorbed by an element – heating up.
Emission spectrum – portion of visible light emitted by that element – cooling down.
CAN YOU / HAVE YOU? • Explain the basics of wave-particle duality.
• Define the relationship between quantum, photon and electron.
• Describe how a produced line spectra relates to the Bohr diagram for a specific element.
Additional KEY Terms
Absorption Spectra