UT Knoxville CHEM 120 - Chapter 6 Reading Notes (4 pages)

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Reading Notes 09 25 2012 Electronic structure arrangement of electrons in atoms Refers to the number of electrons in the atom as well as their distribution around the nucleus and their energies Helps us to understand the arrangement of the elements in the periodic table Quantum theory used to explain behavior of electrons in atoms Quantum physics physics used to describe electrons Light we see with our eyes visible light Electromagnetic radiation carries energy through space radiant energy All move through a vacuum at 3 00 X 10 8 m s speed of light All have wavelike characteristics expressed as up and down movements Wavelength distance between two adjacent peaks or troughs Frequence wavelengths or cycles that pass a given point each second C c is speed of light is wavelength is frequency electromagnetic spectrum shows various types of electromagnetic radiation arranged in order of increasing wavelength Frequency is expressed in cycles per second or hertz Hz s 1 or 1 s Sample Exercise 6 1 A the upper wave has higher frequency because it has shorter wavelength B the upper wave would be visible light and the lower wave would be infrared radiation Sample Exercise 6 2 The yellow light given off by a sodium vapor lamp used for public lighting has a wavelength of 589 nm What is the frequency of this radiation C v v c 3 phenomena are not explained blackbody radiation emission of light from hot objects photoelectric effect emission of electrons from metal surfaces on which light shines emission spectra emission of light from electronically excited gas atoms When solids are heated they emit radiation red glow on electric stove Wavelength distribution of radiation depends on temperature Quantum means fixed amount Smallest quantity of energy that can be emitted or absorbed as electromagnetic radiation E hv h planck s constant 6 626 X 10 34 J s photon packet of energy work function amount of energy require for the electrons to overcome the attractive forces holding them in the