1. Electrons Ms. Hoang’s ACP Chemistry

2. Why electrons?  Determines the atom’s chemical and physical properties  Why some elements are metals and some are nonmetals  Noble gases are inert vs. alkali metals are reactive  Alkali metals tend to form +1 ions  Halogens tend to form -1 ions

3. Wave nature of Light  Light is a type of electromagnetic (EM) radiation  EM radiation: energy that exhibits wavelike behavior and travels through space at the speed of light in vacuum  All electromagnetic waves moves through space at the same constant speed of light  Speed of light = c = 3.00 x 10 8 m/s

4. Characterizing Waves  Three properties: wavelength, frequency, speed  Speed (c):  Wavelength (λ): the distance from one crest to the next  Frequency (ν): is the number of waves that pass a point in a given period of time  Unit: Hertz | 1hz = 1 wave/second

5. Relationship between Wavelength and Frequency

6. Color  the color of light is determined by its wavelength  white light is a mixture of all the colors of visible light  when an object absorbs some of the wavelengths of white light while reflecting others, it appears colored

7. Electromagnetic Spectrum  EM Spectrum: all wavelengths of EM radiation

8. Particle nature of Light  Einstein proposed that the light energy was delivered to the atoms in packets, called quanta or photons  the energy of a photon of light was directly proportional to its frequency

9. Spectra  when atoms or molecules absorb energy, that energy is often released as light energy

10. Flame Test  Is used to ID some metals in compounds.  Each metal gives a flame a characteristic color.  Can identify metals based on flame colors.  Overview: 2 sets of known substances, 2 sets of unknown substances (1-7)  Use water as control (Why?)  Conduct flame test and record your observations (be as detailed as possible, ie bright orange vs reddish orange, faint red vs bright red, yellow green vs blue green, etc.)  Share observations between known group and unknown group  Task: Identify unknown substances 1-7

11. Flame Test