2. Quantum Theory and the Atom

3. In the early 1900s, scientists observed certain elements emitted visible light when heated in a flame. Analysis of the emitted light revealed that an element’s chemical behavior is related to the arrangement of the electrons in its atoms.

4. Niels Bohr’s Model (1913) Electrons orbit the nucleus in circular paths of fixed energy (energy levels).energy levels

5. Energy of Emitted Photon Energy of the emitted photon = Difference in energy between two states

6. Energy emitted by the electron as it leaps from the higher to the lower energy level is proportional to the frequency of the light wave. Frequency defines the color of visible light.

7. Visible light is a type of electromagnetic radiation, a form of energy that exhibits wave-like behavior as it travels through space.electromagnetic radiation

8. The Wave Nature of Light The wavelength (λ) is the shortest distance between equivalent points on a continuous wave.wavelength The frequency (ν) is the number of waves that pass a given point per second.frequency The amplitude is the wave’s height from the origin to a crest.amplitude

9. The Wave Nature of Light (cont.) The speed of light (3.00  10 8 m/s) is the product of it’s wavelength and frequency c = λν

10. Niels Bohr’s Atom Cont’d Electrons can jump from energy level to energy level. Electrons absorb or emit light energy when they jump from one energy level to another.

11. Quantum A quantum of energy is the amount of energy required to move an electron from one energy level to another.

12. The energy levels are like the rungs of a ladder but are not equally spaced.

13. Photons Photons are bundles of light energy that is emitted by electrons as they go from higher energy levels to lower levels.

14. Excited State and Ground State Ground state: the lowest possible energy level an electron be at. Excited state: an energy level higher than the ground state.

16. Emission Spectrum Light emitted produces a unique emission spectrum.

17. Hydrogen Emission Spectrum Violet Blue Red Balmer Series

18. Bohr Model for Hydrogen

19. The Bohr model explained the atomic emission spectrum of the hydrogen atom but did not always explain those of other elements.