1. Emission Spectra and Flame Tests

2. The Big Questions What is light? How is light emitted? What do electrons have to do with light? What are emission spectra? How do flame tests help identify metals?

3. The Electromagnetic Spectrum All light is part of the EM spectrum. Most is invisible: gamma, X-rays, UV, IR, microwaves, radio waves Visible light: wavelength (w.l.) from 400 to 700 nm.

4. The EM Spectrum

5. EM Radiation Light is a carrier or quantum of energy. It is emitted by vibrating charges (like electrons). Light can transfer energy to electrons. Heat can also excite electrons.

6. Energy of Electrons Ground State The lowest possible energy of the electron Excited State Electron that absorbs energy and has moved to a higher energy level

7. Adding Energy Electrons move from a lower energy level to a higher energy level This occurs when the electron absorbs light

8. Light and Electrons Ground state (G.S.) electron Excited state (E.S.) electron Light

9. Losing Energy Electrons give off energy (light) as they move from a higher energy level to a lower energy level Energy of light corresponds to the energy gap between ground state and excite state Sometime the light is visible

10. Light and Electrons Ground state (G.S.) electron Excited state (E.S.) electron

11. Lyman Series Lines at the ultraviolet end of the hydrogen spectrum Electrons move from a higher energy level to n=1

12. Balmer Series Lines in the visible spectrum Electrons move from a higher energy level to n=2

13. Paschen Series Lines at the infrared end of the hydrogen spectrum Electrons move from a higher energy level to n=3

16. Emission Spectrum Emission spectrum – colors of light given off by an element when it is excited (usu. by heat). Every element has an unique emission spectrum.

17. Emission Spectra Hydrogen Helium Carbon

18. Flame Tests Flame test – used to ID some metals in compounds. Each metal gives a flame a characteristic color. Can identify metals based on flame colors.