Why do the lights in Times Square differ from sunlight?

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1 Work hard. Be nice. Name: KIPP NYC College Prep Period: UNIT 3: Electrons Date: General Chemistry Lesson 1: Bright- Line Spectra By the end of today, you will have an answer to: Do NOW: Why do the lights in Times Square differ from sunlight? 1. Determine the ground state electron configuration for: - - Na: - - F: 2. Why would be considered an excited state for Al? _ Compare and contrast the lights in Times Square from other kinds of light like sunlight or even the light from a desk lamp? List one similarity and one difference. _ How do neon lights work? Adapted from do- neon- and- fluorescent- lights- work.html Cool and colorful, eerily radiant, a neon tube emits a light of almost seductive elegance. But mesmerizing as their shimmer may be, neon system owe their glow to nothing more glamorous than a bit of gas and a jolt of electricity. Sealed within the glass tubing of, say, an illuminated signboard is a mixture of gases, one of which will always be neon. Left to itself, neon remains still and colorless. It is only when a current of electricity is passed through the gas that it reveals its garish talents. When such an electrical change is applied, it stimulates electrons circling a neon atom s nucleus. The suddenly excited electrons move farther away from the nucleus. This condition lasts only an instant. Almost immediately, the electrons return to their unexcited state, emitting a burst of energy that is visible, as a brilliant orange- red application of a coating of phosphor powder to the inside of the tube will yield commensurate changes in color. 1. Which subatomic particle plays a role in neon lights? 2. Describe what happens to this subatomic particle in order to produce neon lights?

2 Let s light it up like Times Square! Element Description What colors do you see in your spectroscope? Neon Helium Hydrogen White Light (the ceiling light) REFLECT AND WRITE: 1. Were the colors seen in the spectroscope the same as the color of the lamp? Explain why you think this is based on the article. 2. Do you think all gaseous elements would have unique atomic emission spectra? Explain your answer. 3. What was different about the white light compared to the element lights? Remember: The different lines for each element represent a different color being given off ***How are these lines formed in-terms of electrons and energy:*** Practice Regents Question Identify all the elements in the mixture:

3 Name: Pd: Date: CW 3.2- Bright- Line Spectra 10 points The diagram below shows the characteristic spectral line patterns of four elements. Also shown are spectral lines produced by an unknown substance. Which pair of elements is present in the unknown? 1. lithium and sodium 2. sodium and hydrogen 3. lithium and helium 4. helium and hydrogen Many advertising signs depend on the production of light emissions from gas-filled glass tubes that are subjected to a high-voltage source. When light emissions are passed through a spectroscope, bright-line spectra are produced. Identify the two gases in the unknown mixture. 1. A and B 2. A and D 3. B and C 4. C and D Given the bright-line spectra of three elements and the spectrum of a mixture formed from at least two of these elements: Which elements are present in this mixture? 1. E and D, only 2. E and G, only 3. D and G, only 4. D, E, and G

4 What is the unknown element? SUMMARIZE: What part of the atom is responsible for producing spectral lines and how can spectral lines be used to identify different elements? CRITICAL THINKING: Why do you think every element produces their unique set of spectral lines? Why or why not? 1. Which electron configuration represents the electrons of an atom in an excited state? [1] (1) 2-1 (3) (2) (4) Write an electron configuration for a silicon atom in the excited state. [1] 3. Explain, in terms of subatomic particles and energy states, why light is emitted by a hydrogen atom? [2]

5 Name: Pd: Date: Homework 3.2 Bright- Line Spectra 10 points Put the following words in your glossary: - Bright Line Spectra DIRECTIONS: Read the following passage about fireworks and answer the following questions. Behind the scenes of the dazzling light shows that spectators ooh and ahh at on the Fourth of July, are carefully crafted fireworks. Whether red, white and blue fountains or purple sparklers, each firework is packed with just the right mix of chemicals to create these colorful lights. Inside each handmade firework are small packets filled with special chemicals, mainly metal salts and metal oxides, which react to produce an array of colors. When heated, the atoms of each element in the mix absorb energy, causing its electrons to rearrange from their lowest energy state to a higher "excited" state. As the electrons plummet back down to their lower energy state, the excess energy gets emitted as light. Each element releases a different amount of energy, and this energy is what determines the color or wavelength of the light that is emitted. For instance, when sodium nitrate is heated, electrons in the sodium atoms absorb the energy and get excited. When the electrons come down from the high, they release their energy, about 200 kilojoules per molecule, or the energy of yellow light, according to the website of the University of Wisconsin- Madison chemistry professor Bassam Z. Shakhashiri. The recipe that creates blue, for example, includes varying amounts of copper chloride compounds, while red comes from strontium and lithium salts. Just like paints, secondary colors are made by mixing the ingredients of their primary- color relatives. A mixture of copper (blue) and strontium (red) makes purple. READING COMPREHENSION QUESTIONS: 1. When do electrons release energy? 2. Where does the energy that moves ground state electrons into the excited state in fireworks come from? 3. What two things determine the color of the light that each firework produces? 4. How does this article relate to the concept we learned today in class? 5. How are people s fingerprints similar to the emission spectra for elements?

6 6. Fill out the data table about Neon- 20 Amount of each Mass of each Protons Neutrons Electron Location of each 7. What is the atomic number of Neon- 20? 8. Explain, in- terms of subatomic particles, why Neon- 19 is an isotope of Neon- 20: 9. Determine the ground state electron configuration for Neon: 10. Write one possible excited state electron configuration for Neon: 9. The percent abundance of Neon- 20 is 92%. Another isotope, Neon- 22 has a percent abundance of 8%. Setup, but do not calculate how you would find the average atomic mass for the element Neon. 10. Which list of formulas represents compounds, only? (1) CO 2, H 2O, NH 3 (2) H 2, N 2, O 2 (3) H 2, Ne, NaCl (4) MgO, NaCl, O Two substances, A and Z, are to be identified. Substance A can not be broken down by a chemical change. Substance Z can be broken down by a chemical change. What can be concluded about theses substances? (1) Both substances are elements. (2) Both substances are compounds. (3) Substance A is an element and substance Z is a compound. (4) Substance A is a compound and substance Z is an element. 12. Which particle diagram represents one pure substance, only? ( 1 ) ( 3 ) ( 2 ) ( 4 ) 13. Which grouping of the three phases of bromine is listed in order from left to right for increasing distance between bromine molecules? (1) gas, liquid, solid (2) liquid, solid, gas (3) solid, gas, liquid (4) solid, liquid, gas

7 Name: Pd: Date: Exit Ticket Quiz 3.2- Bright- Line Spectra 2 points 1. Which two elements are in this mixture? (1) barium and hydrogen (3) helium and hydrogen (2) barium and lithium (4) helium and lithium 2. Draw the bright- line spectra for a mixture of hydrogen and lithium: Name: Pd: Date: Exit Ticket Quiz 3.1- Bright- Line Spectra 2 points 1. Which two elements are in this mixture? (1) barium and hydrogen (3) helium and hydrogen (2) barium and lithium (4) helium and lithium 2. Draw the bright- line spectra for a mixture of hydrogen and lithium: