Chem1114 Lab 5 Atomic Spectroscopy Remote Version Su20.pdf...

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Lab 5 – Atomic SpectroscopyAtomic SpectroscopyLab5OBJECTIVES- To learn to use a spectroscope to study the lines in the emission spectra of atoms.- To calibrate the spectroscope in order to convert scale readings into wavelengths; to understandthe calibration process.- To examine the spectral lines of hydrogen in the visible region and correlate these lines tohydrogen electronic transitions.- To study the emission spectra of metals present in salts.INTRODUCTIONSpectroscopyThe interaction of light with matter produces many interesting phenomena that are easily observed ona daily basis.For example, the color of the sky is due to sunlight being scattered by molecules in theair: the shorter-wavelength blue light is scattered more than longer-wavelength red light thus causingthe sky to appear blue.Similarly, a rainbow after a storm is the result of light passing through prism-like raindrops, which break the light into its component colors. A dilute solution of powdered milk(which contains protein macromolecules that can scatter light) appears opalescent blue.In this experiment, you will study the interaction between light and atoms.For most atoms at roomtemperature, the electrons occupy the lowest allowed energy level, known as theground state.Whenatoms are energized by an electric discharge, by a flame, or by light, electrons are excited from thelower level to higher energy levels known asexcited states. These excited atoms can emit photons of aparticular wavelength and drop down to lower energy levels. If the emitted light is passed through anarrow slit and then through a prism or diffraction grating, anemission spectrumis observed.According to quantum theory, the energy content of an atom isquantized;that is, the energy can haveonly certain discrete values.The allowed energy levels are characteristic of each particular kind ofatom.Through the technique ofemission spectroscopy, the allowed energy levels can be probed.Quantum theory describes light as being composed of tiny bundles of energy called photons.Differentcolors of light are produced by photons of different wavelengths.The energy of a photon E is relatedto its wavelengthλby the equation:E=hc/λEquation 1where h is Planck's constant, 6.626 x 10-34J·s and c is the speed of light in a vacuum, 3.00 x 108m/s.From the law of conservation of energy, we deduce that the energy of a photon emitted from an atommust equal the spacing between two allowed energy levels of the atom.Thus, observation of thespectrum of an atom provides direct information about thespacingbetween the allowed energy levelsin the atom.
Lab 5 – Atomic SpectroscopyFigure 1:Operation of the spectroscope and the resulting line spectrumIn this experiment, you will use a spectroscope (Figure 1) to characterize light emission from excitedatoms. In this technique, a narrow beam of light from the source (e.g., a hydrogen discharge tube)enters a collimator through a slit.This beam strikes a grating or prism, which disperses the light.

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Term
Fall
Professor
VeronicaBierbaum
Tags
Atom, Photon, Atomic Spectroscopy

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