Bohr Atom Model and Emission Spectra


From physick.wikispaces.com (Connor Boggs)


Neils Bohr published his model of atomic structure in 1913, and went on to receive the Nobel Prize in Physics in 1922
Neils Bohr published his model of atomic structure in 1913, and went on to receive the Nobel Prize in Physics in 1922


Atomic Model

Bohr made 3 main points with his model:
  1. Electrons orbit the nucleus in orbits that have a set size and energy. They are quantized.
  2. Each orbit relates to a certain energy level, with only electrons with that much energy in that orbit; the closer the orbit to the nucleus, the lower the energy.
  3. An electron moves from orbit to orbit by absorbing or emitting EMR energy.


external image DOE_Nuclear_Bohr_Model_of_the_Atom.gif

Each orbital has it's own number. The first orbital (n=1) is known as the ground state, the second orbital (n=2) is known as the first excited state, etc. A single electron can only occupy a single orbital, and it must have a certain amount of energy for that level. To move down an orbital, and electron will have to lose a certain amount of energy, so it emits energy in the form of EMR. Like wise when moving up energy levels, it will have to gain energy and absorb EMR energy to do so. The larger the jump, the more energy of EMR will be absorbed or emitted.

Bohr calculated the amount of energy needed to move between orbitals using the following formula:

external image 95e3280260efc6b9417f9a22edf57744.png

Where:
E= Energy needed to jump orbitals
h= Plank's constant
c= Speed of light
external image e05a30d96800384dd38b22851322a6b5.png= wavelength of light

Emission Spectra


When electrons move between orbitals, they absorb or emit EMR to gain or lose energy. Since the orbitals are quantized, they need a certain amount of light to move between energy levels. This causes for specific wavelengths of lights to be absorbed and emitted. This can cause emission/absorption spectral lines that can be found using spectroscopy. Each element has their own unique spectral lines, so this can act as a fingerprint for each element.

This is the emission and absorption lines for Hydrogen..
This is the emission and absorption lines for Hydrogen..
References



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