Niels Bohr

1. Visible Hydrogen Spectrum Resulting from the Excitation of H AtomsWavelength 409 nm 433 nm 485 nm 655 nm

2. Niels Bohr Interested in how the electrons moved around the nucleus Approached the problem by focusing on the energy of the electrons based on the emission of light by electrons

3. Emission of Light by Electrons Energy (heat, electricity) is added to a gas sample of an element. “Excitation” Light is emitted by the gas sample. The light is emitted at specific wavelengths characteristic of specific elements.

4. Visible Hydrogen Spectrum Resulting from the Excitation of H AtomsWavelength Energy___ 409 nm 4.86 x 10 –19 J 433 nm 4.59 x 10 –19 J 485 nm 4.09 x 10 –19 J 655 nm 3.03 x 10 –19 J

5. Why were there only specific wavelengths of light produced? Electrons can only occupy certain orbits around the nucleus. Each orbit has a specific energy. An electron could be found in one orbit or another, but never in an area in between two orbits.

6. Excited Electron Falls Back to Lower Energy Level, Emitting Light

7. Bohr Model of the Atom1. Electrons move around the nucleus in circular orbits 2. Only certain orbits are possible 3.Each orbit represents a specific energy level, with energy increasing with increasing distance from the nucleus 4. Each energy level has room for only a specific number of electrons based on its distance from the nucleus

8. Bohr Described the Orbits of the Electrons on the basis of their energy. Bohr’s Equation for the Energy Values of Each Energy LevelE = - 2.18 x 10 -18 Jn 2 1st Energy Level (n=1) E = - 2.18 x 10 –18 J 2 electrons 2nd Energy Level (n=2) E = - 5.45 x 10 –19 J 8 electrons 3rd Energy Level (n=3) E = - 2.42 x 10 –19 J 18 electrons