Lab: Electron Configuration Objectives •
•
Observe the energy emitted from different electron energy levels when energy is applied to a gas-discharge lamp. Obtain a basic knowledge of why gas-discharge lamps produce different colors of light.
Introduction Commonly referred to as “neon lights” or vapor lamps, gas-discharge lamps are foun found d on on the the stor storef efro ront nt s of of mos mostt eve every ry retail business in developed countries. In many Asian Asian countries, countries, such as Thailand, Thailand, colorful gas-discharge lamps are used to adorn temples and other buildings. In America they are most often used as eleme elements nts of of the out outdo do or bus busine iness ss sign signs s for restaurants and movie theaters. You may also see these these decor decorativ ative e light lights s as an accessory on automobiles – in the form form of of runn running ing light light s or lic licens ense e plate plate borders.
Figure 1 : Colorful Colorful g as-dischar as-discharge ge lam ps filled filled with noble gases i ncluding ncluding neon and and argon. The type of gas, sealed in a glass vacuum-t vacuum-tu u be, determines determines the color produced when energy is supplied to the lamp.
Gas-dis Gas-dischar charge ge lamps lamps have hundreds hundreds of uses uses in our modern modern society society:: traffic traffic lights, lights, headlights, street lamps, movie theater projectors, even the tiny lights on computers and other electronics electronics – the LED (li ght emitting diode). Growing Growing env ironmental ironmental concerns over energy consumption and pollution has resulted in a worldwide campaign to use compact fluorescent fluorescent lamps lamps (a type type of gas-discharge gas-discharge la la mp) in place of of the less less energy energy efficient efficient incandescent light bulb. During the period before WWII, gas-discharge lamps were used, unsuccessfully, unsuccessfully, as as tanning lamps lamps in an effort to help reduce reduce high rate rate of child mortality
© KC Distance Learning
due to tuberculosis. High-intensity discharge lamps, which release ultraviolet radiation, are used today in water purification systems to kill bacteria.
Figure 2 : A c ompact fluoresc ent bulb with the exposed b allast. The ballast controls the fre quency of the modul ated cu rrent – a ne cessary compo nent of a gas-discharge lamp.
The two necessary components of a gas-discharge lamp are: a glass vacuum tube containing a noble gas, metal halide, or mixture of those substances and a frequency modulated power supply. The special electric circuitry required to modulate the current of a gas-discharge lamp is known as the “ballast.” In the North America, the ballast is attached to compact fluorescent bulbs but in Europe compact fl uorescent bulbs connect to central ballast.
Figure 3 : A Xenon ga s-discharge la mp as the type us ed in the headlig hts for auto mobiles. Large r versions of Xenon lam ps are u sed in movie proje ctors such a s the Xeno n pulse lam p use d in IMAX projectors.
A gas-disc harge lamp produces light as ener gy, controlled by the ballas t, heats an element releasing electrons and “ionizing” t he gas in the tube. T he free electrons are accelerated by the modulation of the current and collide with a gas or metal atom. When this collisio n occurs, electrons orbiting t he atom can be “excited ” to a higher energy
© KC Distance Learning
state. Excess energy, in the form of light-e mitting photons, is released as the electron falls back to its original orbit. Each “energy level” of an atom is quantized and is the location for a set number of electrons. Electrons can only move to an energy level, they cannot remain between energy levels. So an excited electron can move from the 1s energy level to the 2s energy level but not to the 1.5s energy level. The naming system for describing the location of an electron is broken into three basic parts: the principal energy level (n = 1, 2, 3, 4, 5, 6, 7), the sublev el (s, p, d, or f), and the number of orbitals (elec tron clouds) at that leve l. Known as the “electron configuration”, it is a si mple way for scientist to determine the relative energy of an electron. The amount of energy released as electrons move between the different energy levels, corresponds directly to the wavelength of light produced during the event. Astronomers and chemists use this process to determine the chemical composition of any l ight producing event – as in the burning of gases on a star or the light produced by a gasdischarge lamp. The wavelength of the light emitted duri ng the shift in the electron’s energy level decreases when more energy is released and increas es when less energy is released.
y g r e n E g n i s a e r c n I
Figure 4 : A diagram of the arran gement of orbitals illustrating the energy levels on the lef t, the sublevels on the right, an d the number of electrons (in each orbital) in the center (each arrow represents one electron).
Increasing Energy
Figure 5 : T his scale, di agramming t he color and wavelength of light (as measured in n anometers – nm), illustrates th e na rrow wavelength of Yellow li ght. Located bet ween the enclo sing black vertical b ars, Yellow light has a wavelength of 570-580nm.
© KC Distance Learning
Pre-lab Questions 1. Describe what is meant by the term “electron configuration.” Electron configuration is the rearrangement of electrons of an atom or molecule in atomic or molecular orbitals.
2. How does the electron configuration of an atom relate to the amount of light emitted during an energy releasing event? The electron configuration of an atom relate to the amount of light emitted during an energy releasing event because the brighter the light the more energy is being released, which may alter the arrangement and quantity of electrons in the outer shells within an atom's electron configuration.
3. Describe two other phenomena that produce various wavelengths of light. Two phenomena that can produce various wavelengths of light are heating a substance, causing ionization and, nuclear fission at the center of the sun or stars.
© KC Distance Learning
Experiment: Chemical Gas-Discharge Lamps In this experiment energy released in the photons will be compared to the electron configuration of certain elements contained in a variety of gas discharge lamps. The frequency of the energy supplied to the lamp can be varied and the spectrum of the light produced can be compared to the electron configuration of the material being studied.
Materials •
Gas-Discharge Lamp Simulation
Procedure: Part 1 1. Open the gas-discharge lamp simulation. 2. Leave the energy level on the battery set to 23.00 volts. 3. Be sure the “Electron Production” is set for “Single.” 4. Examine the legend and the discharge lamp device. 5. Under “Options” be sure to check both “Squiggles” and “Run in slow motion.” 6. Observe and record the results in the discharge lamp and on the electron configuration panel as you fire a single electron at each of the four elements listed in the drop-down menu. 7. Select “Configurable” from the drop-down menu and slide the number 2 energy level to a new position up or down the electron configuration. 8. Observe and record the results as you fire a single electron at the “Configurable” material. 9. Repeat Step 8 for three different energy level positions.
© KC Distance Learning
Data and Observations: Part 1 Gas-Discharge Lamps: Results of Energy Discharge – Single Electron Substance
Observations The hydrogen atom passed right through the other atom and produced a charge of about 2 and shed 1 photon
Hydrogen
The atom hit the mercury and continued while the mercury got a charge of between 3 and 8 and then shed between 1-4 photons
Mercury
The atom hit the sodium giving it a charge of 6 and then the sodium shed 4 photons
Sodium
The atom hit the neon and there was no charge so no photons were shed
Neon
The atom hit and gave a charge of 2 before the larger atom shed 1 photon
Configurable
© KC Distance Learning
Procedure: Part 2 1. Leave the energy level on the battery set to 23.00 volts. 2. Set the “Electron Production” to “Continuous.” 3. Under “Options” check only “Spectrometer.” 4. Adjust the electron production to 70% by moving it to the right. 5. Observe and record the different wavelengths produced in the spectrometer for each of the four elements.
Data and Observations: Part 2 Gas-Discharge Lamps: Results of Energy Discharge – Substance
Hydrogen
Mercury
Sodium
Neon
Continuous Electrons
Observations Atoms hit the hydrogen at very fast rate but it only holds up to 6 charge before it has to shed at least 1 photon
Atoms hit the mercury at very fast rate but it only holds up to 9 charge before it becomes necessary to shed at least 1 photon
Atoms hit the sodium at very fast rate but it only holds up to 6 charge before it needs to shed at least 1 photon
Atoms pass through the neon at very fast rate but the neon does not react
© KC Distance Learning
Procedure: Part 3 1. Switch from “One Atom” mode to “Multiple Atoms” mode. 2. Be sure the “Electron Production” is set for “Continuous.” 3. Under “Options” check only “Spectrometer.” 4. Select “Neon” from the drop-down menu. 5. Manipulate the energy supply and the percentage of continuous electron production to produce the greatest level of “red” light.
Data and Observations: Part 3 Gas-Discharge Lamps: Results of Energy Discharge – Neon Lamp Substance
Observations between 500 and 600 with some exceptions of reaching above 600.
Spectrometer Readings 23
Voltage Level 100%
Percentage of Electron Production what I've notice is that most neon atoms at the end of the bar are obtaining and maintaining their charge. The photons are helping to light up even more then before and producing different photon charges.
Other Observations
© KC Distance Learning
Post-lab Questions 1. Write out the electron configurations of each the materials used in your gasdischarge lamps. Potassium is already done as an example for you. HINT: The periodic table is very helpful and can be used as guide. MATERIAL
ELECTRON CONFIGURATION 2
Hg
2
6
2
6
1
1s 2s 2p 3s 3p 4s
1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^2 4p^6 4d^10 5s^2 5
Na
1s^2 2s^2 2p^6 3s^1
Ne
1s^2 2s^2 2p^6
2. What is the approximate wavelength of light emitted by each of the materials?
MATERIAL
COLOR
WAVELENGTH
H
red
656.2 nm
Hg
blue
436 nm
Na
Yellow
589 nm
Ne
green
540.1 nm
3. On the bottom of the simulation screen, click on the button to view actual images of gas-discharge lamps and neon lights. Notice the lamps containing Neon gas can be different colors – how is this possible? The different charges and environmental factors in each can be different resulting in varying colors.
4. What must occur in order for a gas-discharge lamp to produce light? What must occur in order for a gas-discharge lamp to produce light is by creating an electrical discharge through ionized gas.
© KC Distance Learning
