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UCM CHEM 002-01 - lab report 1

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1) Introduction: The purpose of this lab is to measure the wavelength of the Balmer line in the hydrogen–atom spectrum and measuring the visible flame emission spectrum of atomic lithium and sodium. Evaluate the pattern of energy states and describe by the hydrogen Balm lines with respect by the principle quantum number, n, describing the states, and investigate electron repulsion in multi-electron atoms as a function of the azimuthal quantum number, l, by determining the effective nuclear charge (zeff) and radius (reff) for the valance orbitals of atomic and sodium from their emission spectra.2) Experimental:a) Materials:Ocean optics spectrometer with fiber optic probe: hydrogen gas discharge tubewith power supply; Nichrome were inserted in cork; Bunsen Burner; usb transfer drive and/ or computer configuration with Microsoft Excel and a printer.Chemicals: solid lithium and sodium chloride in labeled vials; 6 M hydrochloric acid in dropper bottles with accompanying small test tubes (for cleaning Nichrome wires).b) Apparatus:c) Procedure: H-atom Spectrum1) Put the fiber optic probe of the ocean optics spectrometer near the output on the discharge tube.2) Measure the hydrogen emission spectrum using the spectrometer.3) Position the fiber-optic probe until the most extreme transition (around 650nm) has an intensity right between 65,000 counts. 4) Save the spectrum recovered to your flash drive to process it later on in Microsoft Excel.5) A recording of another spectrum may be required to be able to ultimately decide the wavelengths for all four lines of the hydrogen emission spectrum. Write down and print data from Microsoft Excel later on to include in the report.Metal-Ion Flame Tests6) Clean the Nichrome wire by consecutive dipping the wire into a test tube containing 6M HCL.7) Heat the wire in the hot part of the Bunsen burner flame until the yellow ccolor, representing sodium contamination is no longer visible. 8) Acquire pea-sized allotments of Solid metal chloride salts: Li(cs), NaCl(cs) 9) Position a sample of each salt on the tip of the Nichrome wire that is labeled fta10) Place the wire containing each salt sample in the hot portion of the Bunsenburner flamePage 1 of 211) Observe the emission colors for each salt in the flame of the Bunsen burner12) To record the emission colors of various salts, dim down the lights of the room. 3) Results and Discussion:1) According to Bohr diagram, when an electron jumps from the orbital n=6 to n=2, a photon of light shoots out 292 KJ/mol of energy. Similarly, when an electron hops from the orbit n=5 to n=2, a photon of light shoots out 276 KJ/mol of energy. Also, when an electron jumps from orbits n=4 and n=3 to n=2, 246 KJ/mol and 182 KJ/mol of photon light energy is emitted.2) Chloride Salts Color Wavelength IntensitiesNaCl Bright yellow 591nm 42,000 countsLiCl Vibrant pinkish red 670nm 61,6265 counts3) Photon EnergyLithium: E= 178KJ/molWavelength=670X10^-9mSodium: Wavelength=589X10^-9mE= 203KJ/molWavelength=591X10^-9mE= 202KJ/molLithium Diagram orbital in notebookLithium Diagram orbital in notebook4)Zeff Reff Shielding ParameterLi2s 1.26p+ 4.76ao 1.74+Li2p 1.02p+ 4.90ao 1.98+Na3s 7.34p+ 8.80ao 9.58p+Na3d 13.3p+ 13.3ao 10.2p+4) According to my Observations, for sodium, as you go higher in the orbital subshells, the effective nuclear charge (Zeff) decreases. On the other hand, as you go in the orbital subshells for sodium, the radius of the orbitals (reff) increases. The shielding parameter also increases as you move up the orbital subshells for sodium. This essentially means as electrons go in the outer orbits, the core electrons will shield theses valances electrons further away from shield theses valence electrons further away from the nucleus, with the positive charge of the nucleus being low, resulting in the nucleus not having a strong pull on the electrons. Page 2 of


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UCM CHEM 002-01 - lab report 1

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