Activity 5: The Electronic Behavior of Atoms

1. Activity 5: The Electronic Behavior of Atoms Chapter 1 What do those colors mean???

3. Bohr’s “Planetary Model” • Electrons are in fixed energy levels around the nucleus • Energy levels get closer together as they get further from the nucleus. • Think of a ladder that isn’t equally spaced +

5. Where are electrons located? • Energy levels: • Regions around the nucleus where electrons can be found • Electrons can move from one energy level to another by gaining or losing energy

7. Video Bohr Tower

8. The nature of Light What’s going on here???

9. Waves crest trough The wavelength is the distance from the crest (top) of one wave to the crest of the next.

10. The frequency of a wave is defined as how many cycles of a wave pass through a point per second. The frequency (υ) and the wavelength (λ) are inversely relatedthrough the equationthe speed of light (c)= λ υA relationship between two numbers in which an increase in the value of one number results in a decrease in the value of the other number. The shorter the wavelength = the higher the frequency Short wavelength Long wavelength

11. The electromagnetic spectrum Wavelength decreases, frequency increases, Energy increases

12. Visible Region Long wavelength Low frequency LOW ENERGY Small wavelength High frequency High ENERGY An increase in the frequency of the wave and an increase in energy of the wave. As you move from Red to Violet light, the wavelength of the waves decreases.

14. What does this mean? Colors of light are associated with energy. Red light has the least energy, while violet light has the most energy.

15. Explain this cartoon…..

16. Why is the Sky Blue? Sunlight reaches Earth's atmosphere and is scattered in all directions by all the gases and particles in the air. Blue light is scattered in all directions by the tiny molecules of air in Earth's atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.

17. Why is the Sky Blue? Why not violet?

18. Why are Sunsets Red? As the Sun gets lower in the sky, its light is passing through more of the atmosphere to reach you. Even more of the blue light is scattered, allowing the reds and yellows to pass straight through to your eyes.

19. Why are Sunsets Red? http://news.discovery.com/videos/why-tell-me-why-why-is-the-sky-blue.html

20. Dan Flavin

22. How did Niels Bohr arrive at his model? Flame Test Experiment

23. Bohr observed the flame colors through an instrument that separates the light into its component colors---just like a prism!

24. Spectroscope

25. Slit (light enters here) Grating diffracts light, separating colors Light source Wavelength scale Look in here This is the spectrum you would observe if you used a spectroscope to look at a white computer screen. How a spectroscope works

26. ATOMIC EMISSION SPECTRUM When the flame colors are observed through a spectroscope, a pattern of bright lines appears

27. The bands of light are called: ATOMIC EMISSION SPECTRUM All elements have a DIFFERENT pattern of spectral lines that can be used to identify the element. This spectrum is unique to every element. ATOMIC EMISSION SPECTRUM

28. Why do we see this? • Electrons can get “excited” and move from lower energy levels to higher energy levels by absorbing energy. • When they fall back down to a lower energy level the electron loses energy in the form of light. ATOMIC EMISSION SPECTRUM

29. Atomic Emission Spectrum Add energy

30. So… • Electrons start off in the GROUNDSTATE • They absorb energy and move to the EXCITED STATE • They then lose this absorbed energy fall back down to the groundstate and emit light!