<p>Honors Chemistry Name ______</p><p>Chapter 11: Emission Spectroscopy Lab Date _____/_____/_____ Period _____</p><p>Pre-Lab Discussion The normal electron configuration of an atom or ion(s) of an element are known as the “ground state”. In the most stable energy state, all electrons are in the lowest energy state possible. (According to the AUFBAU Principle, electrons will occupy the lowest energy state possible.) When energy is added to an atom or ion, the electrons of the atom or ion may absorb enough energy to allow them to “jump” to a higher energy state, called the “excited state”. The atom or ion is said to be in an excited state. This excited state configuration is not stable and the electrons return to their normal ground state, releasing energy in the form of electromagnetic radiation (EMR). Some of this EMR may have wavelength that allows us to see the energy as visible light. The color of this light can be used as a means of identifying the elements involved.</p><p>Purpose Metals, with their loosely held electrons, are excited in the flame of a laboratory burner. Gases can be excited by running high voltage through the gaseous atoms under low pressure. In either case, the excited atoms will, in each case, produce a characteristic spectrum. The goal of this lab is to excite metal ions or gaseous atoms, record the gross color of emitted light, use spectroscopes to get a more complete emission spectrum from light sources and the bright-line spectra of some gaseous elements, and calculate the energy of released photons.</p><p>Safety  Do NOT touch the high-voltage power supply.  Follow appropriate procedures when operating the burners. Tie back long hair and secure loose clothing.  Many of the salts used in this experiment are toxic. Be sure to wash your hands thoroughly after coming into contact with any of the substances.</p><p>Procedure Part I – Emission Spectra of Gaseous Elements</p><p>1. Using a spectroscope, examine the spectrum emitted by an incandescent light source. Record your observation by sketching the continuous spectrum. Record all the colors and the relative amounts of each present.</p><p>2. Aim your spectroscope at a fluorescent light source. Record your observation by sketching the continuous spectrum. Record all the colors and the relative amounts of each present.</p><p>Part II – Emission Spectra of Gaseous elements View each gas tube and record its gross color (what you see with just your eyes) beneath its name in the Part II Data Chart. View each of the following gas tubes using a spectroscope. Record the line spectrum in the top half of each box in the chart (Part II Data Chart). If you see one red line, then draw one line in the box below “Red” for the gas tube that you are viewing. If you see two red lines, then draw two lines in the box below “Red” for the gas tube that you are viewing. After viewing all of the gas tubes and recording their observed line spectrums in the top half of each box in the chart, refer to a wall chart to obtain and record the accepted line spectrum of each gas in the bottom of each box. Part III – Flame Tests of Metal Ions</p><p>1. Using the striker, ignite a Bunsen burner. Adjust the burner so that the flame is almost invisible.</p><p>2. Note: Be sure that the wire loop is correctly matched to the correct chemical before using it! a. If the chemical (salt) is solid, moisten the wire loop in some distilled water. Then dip the loop in the solid chemical so that some of the chemical sticks to the loop of the wire. b. If the chemical (salt) is liquid, dip the wire loop in the liquid chemical so that it moistens the loop of the wire.</p><p>3. View the flame test of each salt and gross color (what you see with your eyes) just beside its name in the Part III Data Chart A.</p><p>4. Repeat Steps 2 and 3 using the other salts of known identity. To prevent contamination of the samples, be sure to use each loop for only one salt.</p><p>5. Record the number of the unknown chemical for your lab group in Part III Data Chart (example: U5). The unknown is one of the chemicals used in Part III. Repeat steps 2 and 3 using the unknown salt.</p><p>6. Compare the line spectrum of the unknown salts to the line spectrum of the known salts and determine the identity of the unknown salt. Record the identity of the unknown salt in Part III Data Chart A.</p><p>7. After viewing all of the flame tests of the salts, refer to a wall chart to obtain and record the accepted line spectrum of each salt in Part III Data Chart B.</p><p>Questions</p><p>1. What form of energy emission accompanies the return of excited electrons to the ground state?</p><p>2. Explain why metal atoms can be excited using a Bunsen burner whereas gaseous atoms need a high voltage power source?</p><p>3. What happens to the distance between successive energy levels as the number of energy levels increases? What happens to the energy difference between successive energy levels with each additional energy level? </p><p>4. What are some practical applications of spectroscopy? Your answer should be thorough and reflect research done on your part.</p><p>Observations Record your observations as directed in the procedure.</p><p>Part I Fluorescent light Incandescent light Part II Data Chart: Gas Tube Line Spectrum Gas Tube Red Orange Yellow Green Blue Indigo Violet (Gross Color) Helium Observed</p><p>Accepted</p><p>Hydrogen Observed</p><p>Accepted</p><p>Krypton Observed</p><p>Mercury Observed</p><p>Accepted</p><p>Neon Observed</p><p>Air Observed</p><p>Part III Data Charts: Flame Test A. Gross Color (All work for the calculations must be included in your write-up.) Substance Gross Color Wavelength Frequency Energy (in meters) (in Hertz) (in Joules)</p><p>Ba(NO3)2</p><p>Ca(NO3)2</p><p>Cu(NO3)2</p><p>KNO3</p><p>LiNO3</p><p>NaNO3</p><p>Sr(NO3)2</p><p>Unknown Chemical: B. Emission Spectra of the Seven Metal Ions Metal Ion Red Orange Yellow Green Blue Violet Accepted Barium Accepted Calcium Accepted Lithium Accepted Sodium Accepted Strontium </p>