The Bohr Model

Published on Sep 28, 2016

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PRESENTATION OUTLINE

The Bohr Model

Ethan,Madyson,Rileigh
Photo by ** RCB **

wave theory of light

  • during the 18th century, philosophers and scientists had a heated debate over whether light is particle like or something else entirely.
  • in his 1704 treatise opticks, Newton compared light to weightless balls rebounding off a smooth surface
  • Newton's hypothesis provided a convincing explanation of reflection, but did not explain how light bends though a prism
  • in 1803 Thomas Young discovered a phenomenon known as double slit interference, in which light passing through two thin parallel slits produces a pattern of bright and dark fringes on a screen

atomic spectra

  • When atoms are excited they emit light of certain wave lengths which correspond to different colors. The emitted light can be observed as a series of colored lines with dark spaces in between; these series of colored lines is called an atomic spectra.
Photo by TonZ

What is an excited atom?

  • An excited atom is when the quantum state of the system (a atom molecule or nucleus) is higher than the ground level of energy.

There is 2 types of atomic spectra.

  • The emission spectrum: a set of wavelengths emitted by excited atoms.
  • the absorption spectrum: this is created when white light is passing through a collection of atoms.
Photo by Ricecracker.

Atomic spectroscopy

  • This is the process of analyzing spectral lines to identify the chemical make up of a sample
  • This was actually used to analyze a then unknown spectral lines coming from the sun these lines belonged to an element they soon called helium.

The Bohr Model of Hydrogen

  • in 1913, Neils Bohr showed a model of the hydrogen atom
  • he attempted to show why energy emitted from atoms is quantized
  • Bohrs hypothesis had several key assumptions

Bohrs Key Points

  • Electrons revolve around the nucleas in a circular orbit
  • electrons can only occupy certain stable orbits or energy levels at a specific distance from the nucleas
  • electrons can miove to higher energy levels by absorbing electromagnetic radiation or move too

energy levels

  • Bohr was able to predict the energy levels of the hydrogen atom, which were indexed by the quantum number n=1,2,3 etc.
  • The lowest allowable energy state, for which n=1, is known as the ground state of the atom.
  • the lowest allowable energy state, for which n=1, is known as the ground state of the atom
  • in this state, the electron is also closet to the nucleus. as the quantum number increases, the difference in energy between successive hydrogen levels becomes progressively smaller.
  • a more general understanding of the principles of energy and angular momentum quantization were needed before physicists could fully understand the electron orbital structure of atoms

the de broglie hypothesis

  • The De Broglie hypothesis is the theory of all matter could be treated like having a wave like characteristics, much like waves of light.
  • basically he said that every piece of matter has an associated wave legth
show the equation
h= planks constant= 6.62607004 x 10 to the power of negetive 34

p= the momentum of the matter
De broglie wave length sign
Photo by fo.ol

explaining the theory

  • Its talking about seeing matter as waves instead of particles.
  • For example: if you send electrons through an aperture (opening or door way) and put a screen outside the aperture, and when the electrons hit it you would expect it to make a tiny dot because we would think electrons as tiny bullets. but that's not what happens. the electrons make a diffraction pattern, which is something waves do. Why do they do that?
Photo by Pietro Zuco

particle and wave
-these names are Just very useful concepts we use the help us understand things better.

Photo by highersights

why haven't we discovered this before

  • well the only time we can see it happen to an e- is when the aperture it passes through is the size of the de broglie wavelength
  • which is 10 to the negetive 8th power small in meters which is much smaller than the apertures we see in our commom day life

wave particle duality

Jaclyn Nielsen

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