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 Tweet # AP Chemistry - Bohr Model

Introduction: When you think of fireworks, how do you think that they are created? The answer lies in an understanding of the Bohr Model, a model of the atom that emphasizes the existence of circular pathways called orbits, that travel in specific energy levels around the nucleus of an atom. These orbits are much like the orbits represented in the solar system shown in the image above. Specifically, when an electron in a heated salt moves from a higher energy level to a lower energy level, energy is emitted (or released) in the form of light with a specific wavelength. The specific wavelength of the energy released corresponds to specific colors that you may see in fireworks.

For each specific numbered orbit, there is a specific amount of energy associated with it, which is given by the following equation:
$E_n=-2.178 xx 10^-18 J (Z^2/n^2)$,
where n=an integer, Z=nuclear charge, J=energy in joules

One limitation, however, of Bohr’s Model is that it generally only applies to hydrogen atoms, so its accuracy is limited when it comes to more complex elements, like lithium and sodium. Furthermore, electrons generally do not move in circular orbits around the nucleus of an atom.

What’s especially interesting about the Bohr Model is that the energy associated with an electron moving from a higher energy state to a lower energy state can be calculated by finding the mathematical difference in the energies of different energy levels. Generally, the energy change associated with moving to a higher energy state will be positive, while the energy change associated with moving to a lower energy state will be negative.