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Bohr Model of the Atom

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making the crucial assumption that not all of the classical ... allowed states = stationary states. lowest = ground state n = 1 ... – PowerPoint PPT presentation

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Title: Bohr Model of the Atom


1
Bohr Model of the Atom
  • Neils Bohr (1885-1962) developed a new model of
    H-atom by
  • making the crucial assumption that not all of the
    classical
  • physical laws apply to the atomic scale.
  • Bohrs Postulates
  • 1. Energy of H-atom is not a continuous function
    it can only exist in a limited number of
    discreet energy states---the energy is quantized!
  • allowed states stationary states
  • lowest ground state n 1
  • others excited states n 2, 3, 4...

2
Bohr Model of the Atom
  • Neils Bohr (1885-1962) developed a new model of
    H-atom by
  • making the crucial assumption that not all of the
    classical
  • physical laws apply to the atomic scale.
  • Bohrs Postulates
  • 1. Energy of H-atom is not a continuous function
    it can only exist in a limited number of
    discreet energy states---the energy is quantized!
  • allowed states stationary states
  • lowest ground state n 1
  • others excited states n 2, 3, 4...
  • 2. The atom does not radiate energy as long as it
    remains in a stationary state
  • absorbs E goes from lower to higher state
  • emits E goes from higher to lower state

3
Bohr Model of the Atom
  • Neils Bohr (1885-1962) developed a new model of
    H-atom by
  • making the crucial assumption that not all of the
    classical
  • physical laws apply to the atomic scale.
  • Bohrs Postulates
  • 1. Energy of H-atom is not a continuous function
    it can only exist in a limited number of
    discreet energy states---the energy is quantized!
  • allowed states stationary states
  • lowest ground state n 1
  • others excited states n 2, 3, 4...
  • 2. The atom does not radiate energy as long as it
    remains in a stationary state
  • absorbs E goes from lower to higher state
  • emits E goes from higher to lower state
  • 3. The different states correspond to different
    orbits of the electron.

4
Bohr Model of the Atom
  • Neils Bohr (1885-1962) developed a new model of
    H-atom by
  • making the crucial assumption that not all of the
    classical
  • physical laws apply to the atomic scale.
  • Bohrs Postulates
  • 1. Energy of H-atom is not a continuous function
    it can only exist in a limited number of
    discreet energy states---the energy is quantized!
  • allowed states stationary states
  • lowest ground state n 1
  • others excited states n 2, 3, 4...
  • 2. The atom does not radiate energy as long as it
    remains in a stationary state
  • absorbs E goes from lower to higher state
  • emits E goes from higher to lower state
  • 3. The different states correspond to different
    orbits of the electron.
  • 4. Energy emitted or absorbed is quantized
    because the energy states are quantized ?E
    h?

from Plancks Einsteins work
5
Bohr Model of the Atom
  • 1. Energy of H-atom is not a continuous function
    it can only exist in a limited number of
    discreet energy states---the energy is quantized!
  • lowest ground state n 1
  • others excited states n 2, 3, 4...
  • 2. The atom does not radiate energy as long as it
    remains in a stationary state
  • absorbs E goes from lower to higher state
  • emits E goes from higher to lower state
  • 4. Energy emitted or absorbed is quantized
    because the energy states are quantized ?E
    h?

6
Energy of a Bohr Orbit
orbit
  • from classical physics
  • E -e2 r n2h2
  • 2r
    4?2me2
  • so, En -2?2me4 -RHhc
  • n2h2 n2
  • ?

Plancks constant
charge
orbit radius
mass
From this, can derive Balmer equation!
7
Bohr Model Energy States for Hydrogen
Bohr (Quantized) model can explain line spectra
for hydrogen.
8
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