Emission Spectra Labdoc发射光谱labdoc.doc

Emission Spectroscopy Name:_Learning Target: Describe the process of excitation and emission of energy by an electron.The development of atomic theory in the late 1800s and early 1900s hinged largely on observable phenomena. The use of atomic emission spectra became the basis for many models of the atom and is vital in the understanding of energy levels and orbital theory. The following websites are useful in understanding the background of the theory and development of atomic emission spectra:/atom7.htm/od/analyticalchemistry/a/flametest.htm/docs/science/how_l1/spectra.html*Use these websites and answer the pre-lab questions. Please submit your answers to the Google form at the following link: http:/bit.ly/18NQuBj. *I will send you all an email with the third link because you cannot reach it by typing in the URL.PART 1: Spectroscopic Analysis of Household Sources of LightMaterials:spectroscope and colored pencilsProcedure:1.Obtain a student spectroscope and examine the spectrum emitted by a household light source. 2.Record your observations on the Report Sheet, remembering to describe the spectrum in words.PART 2: Spectroscope Analysis of GasesMaterials:spectrum tubeshigh voltage power supplyspectroscopecolored pencils Safety Alerts:high voltage; breakablesProcedure:1.Since the high voltages required for this part of the experiment may present an electrical hazard, you should not touch the spectrum tube or high-voltage assembly.2.Once the power supply is turned on aim the spectroscope at the glowing tube. Read the numbers where each spectrum line occurs in your spectroscope. Record these positions on the Report Sheet.3.Using colored pencils, make a sketch of the spectrum on the Report Sheets spectroscope graph. Note the colors that are most bright and the colors that are most dim.4.Once the entire class has recorded the spectrum for this gas, the spectrum tube will be changed. Repeat Step 2 for each of the gas samples and record your observations on the Report Sheet.PART 3: Metal Ion Flame TestsMaterials:Bunsen burnermatchessamples of saltsSafety Alerts:goggles; open flameProcedure:1.CAUTION: Before you use the burner, check to see that safety is observed. Ignite a laboratory burner. Adjust the burner so that the flame is as blue as possible no yellow.2.Dip a cotton swab in one of the solid chemicals. Hold the swab in the flame of your burner. Observe and record the color of the flame as the cotton swab burns. Record the identity of the metal ion and its observed color on the Report Sheet.3.Repeat Step 2, using other metal ions. Record the color of each flame on your Report Sheet.4.Identify the metal ions present in the unknown samples shown by your instructor. 5.Before you leave the laboratory, check to see that the gas valve is completely shut off. Wash your hands thoroughly with soap and water.Report SheetEmission SpectroscopyName: PRELAB QUESTIONS1.According to Bohrs atomic model, where may an atoms electrons be found?2.How do electrons become “excited?”3.What form of energy emission accompanies the return of excited electrons to the ground state?4.What colors would you predict to see from flame tests with the following metal ions:sodiumlithiumpotassiumstrontiumbarium5.Describe the difference between a continuous spectrum and emission spectrum.6.When dark lines appear in a spectrum, what does that indicate?Spectroscopic AnalysisPart I: Spectroscopic Analysis of Household Sources of LightSample: Sample: Sample: Sample: Sample: Part II: Spectroscope Analysis of Gaseous ElementsSample: Sample: Sample: Sample: Sample: Flame TestsPart III: Metal Ion Flame TestsMetal IonFlame Test ObservationsQuestions:1.Compare the results of the various element spectra from Part II with the spectrum observed using the standard fluorescent light tube. Based on your results, what element do you think is used in fluorescent light tubes? Why?2.Was there any difference between the compact fluorescent light bulb and the standard fluorescent light tube? Why or why not?3.Read page 100 in your Chemistry textbook. Answer the Applying Concepts questions #1 and #2 here:#1#24.During a flood, the labels from three bottles of chemicals floated away. The unlabeled bottles of white solids were known to contain the following: strontium nitrate, ammonium carbonate, and potassium sulfate. Explain with detail a method for relabeling these three bottles. (i.e. how will you know which one is ammonium carbonate?) 5.Prior to its discovery on Earth, heliums existence was first confirmed in the sun. View this website (/helium/history.html) and summarize how helium was discovered in the sun using spectroscopy.6.View the website: /teacherslab