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The Bohr Model Purpose To explain the hydrogen line emission spectrum To explain why atoms of hydrogen give off light
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Models of the Atom
Chapter 4 Chm 1.1.2 and 1.1.3
Model: Neils Bohr
• e- circles nucleus in allowed paths, “orbits”• Each orbit has a fixed energy• e- cannot exist between energy levels• e- in orbit farther from nucleus have higher
energy• e- in orbit closest to the nucleus have
lowest energy
The Bohr Model Purpose
• To explain the hydrogen line emission spectrum
• To explain why atoms of hydrogen give off light
The Hydrogen Line Emssion Spectrum
• Pink light emitted from hydrogen when exposed to electric current
• Specific wavelengths and frequency of light
• Electromagnetic radiation - LIGHT
Light
• Electromagnetic radiation
• Gamma, Xrays, UV, Visible, IR, Microwaves and Radio waves
• Visible Light: Violet, Blue, Green, Yellow, Orange and Red
• Wavelength (λ) – distance between 2 wave peaks (m or nm)
• Frequency (ν) – the number of wave peaks per second (Hertz)
• Photon – a particle of electromagnetic radiation having no mass and carrying a quantum of energy
• Quantum – the minumum amount of energy that can be lost or gained by an atom
How atoms give off light…
Using the Bohr Model to predict light
• Example:– What color light is emitted by the hydrogen
atom when an electron transitions from n = 3 to n = 2?
– What wavelength is released when an electron falls from n = 4 to ground state
– What type of electromagnetic radiation is released when an electron falls from n = 4 to n = 3?
Particle Wave-Duality
• Electrons are made of particles (photons)
• They exhibit wave behavior
The Quantum Model
• The electron cloud model• The Heisenberg Uncertaininty principle – it is
impossible to know exact location of electron• Only a probably location is known• Electron do not orbit 2D• Electron are found in a probable 3D region of
space around the nucleus• Probability Model
Bohr vs Electron Cloud