Electrons Ms. Hoang’s ACP Chemistry
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
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
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
Relationship between Wavelength and Frequency
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
Electromagnetic Spectrum EM Spectrum: all wavelengths of EM radiation
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
Spectra when atoms or molecules absorb energy, that energy is often released as light energy
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
Flame Test