Unit 2 Atomic Structure

Unit 2 Atomic Structure Big Idea: Atomic structure explains patterns in the behavior of elements and allows us to predict the chemical and physical behavior of a given element. The organization of elements on the periodic table reflects trends in both atomic structure and element properties. Lesson 1 Lesson 2 Pre-Assessment activity: What does an atom look like? Lab: Law of Definite Proportions (Mg + Cu(C2H3O2)2 Cu + Mg(C2H3O2)2) Group activity: Model of the atom Take 1: Create an atomic model using lab data Law of Definite Proportions Dalton s Atomic Theory Lesson 3 Lesson 4 Lesson 5 Lesson 6 Lesson 7 Lesson 8 Lesson 9 Lesson 10 Lesson 11 Lesson 12 Lesson 13 Lesson 14 Thomson and Cathode Rays Model of the Atom Take 2 Rutherford and Gold Foil Model of the Atom Take 3 Hydrogen Emission Spectrum Electron Energy and Light Model of the Atom Take 4 Electromagnetic Spectrum Energy, Frequency, Wavelength Flame Test Lab Build an Atom PhET simulation protons, neutrons, electrons Isotopes and Atomic Mass PhET simulation Calculating Average Atomic Mass Beaninum lab Electron Configurations Model of the Atom Take 5 Cracking the Periodic Table code Electron Configuration Practice Patterns in Valence Electrons Ions Patterns on the Perioidic Table Mendeleev s ideas Coulombic Attraction POGIL activity Periodic Trends graphing activity

Names Period CHEMISTRY LAB BEANIUM Isotope Analogy Learning goals: Students will explore the concept of isotopes and average atomic mass using an analogy use their ideas in other situations Directions: Obtain a sample of beanium atoms from stock container. Sort the beanium atoms into three groups, each group representing a different isotope. In the observation section, sketch a picture of each beanium isotope to distinguish between each isotope. Fill out the Recording and Calculations section using appropriate units. Recording Data and Calculations: A. Initial observations: Number of type one Beaniums (isotope-1) Number of type two Beaniums (isotope-2) Number of type three Beaniums (isotope-3) B. Calculate the total number of beans Sample calculation here: C. Calculate the percentage of each type of isotope. Percentage of Beanium-1 sample calculation here: Percentage of Beanium-2 Percentage of Beanium-3 D. Calculate the average mass of each isotope. Total mass of type one Beans Average mass of Beanium-1 Sample calculation here: Total mass of type two Beans Average mass of Beanium-2 Total mass of type three Beans Average mass of Beanium-3 Application of isotope type problems 1. 140 students participated in a knowledge retrieval session. 25 scored 90 out of 100; 63 scored 80 out of 100; 31 scored 70 out of 100; 15 scored 60 out of 100; 6 scored 50 on the knowledge retrieval session. Determine the average score on this knowledge retrieval session. Show all work. 2. Magnesium consists of three isotopes with masses of 23.98 (78.6%), 24.98 (10.1%), and 25.98 (11.3%). Calculate the average atomic mass of Mg. Show all work. 3. Copper consists of two isotopes, one with a mass of 62.96 and 70.5% abundant. The other isotope has a mass of 64.96. Determine the atomic mass of Cu. Show all work. Trish Loeblein 8/18/12 (I am unsure of the origin of this lab. I have made many changes my appreciation to the unknown original author)

TITLE Build an Atom AUTHORS Timothy Herzog (Weber State University) Emily Moore (University of Colorado Boulder) COURSE General Chemistry I TYPE In-Class Guided-Inquiry Activity TEACHING MODE Facilitated Group Inquiry LEARNING GOALS Students will be able to: Use information about the number of protons, neutrons, and electrons to: o Identify an element and its position on the periodic table. o Determine whether an atom is neutral or an ion. o Predict the charge and determine the mass of an atom or ion. Relate the number of protons, neutrons and electrons to representations, including atomic symbols and the symbols found on the periodic table. Explain: element symbol, charge, atomic number, mass number, and isotope. COPYRIGHT This work is licensed under a Creative Commons Attribution 4.0 International License. This license allows users to share and adapt the materials, as long as appropriate attribution is given (with a link to the original), an indication if changes have been made, and an indication of the original licensing. BUILD AN ATOM 1

BUILD AN ATOM PART I: ATOM SCREEN Build an Atom simulation (http://phet.colorado.edu/en/simulation/build-an-atom) 1. Explore the Build an Atom simulation with your group. As you explore, talk about what you find. 2. a) List two things your group observed in the simulation. b) What particle(s) are found in the center of the atom? Commented [TH1]: This style of question encourages students to complete a full exploration of the sim and to articulate their findings, without needing the teacher to give instructions for each interaction. The teacher could ask students to share out their list with the class. Minimal (or no) instructor introduction is required before students begin the activity and sim exploration. 3. Play until you discover which particle(s) determine(s) the name of the element you build. What did you discover? 4. What is the name of the following atoms? a) An atom with 3 protons and 4 neutrons: b) An atom with 2 protons and 4 neutrons: c) An atom with 4 protons and 4 neutrons: 5. Play with the simulation to discover which particles affect the charge of an atom or ion. a) Fill in the blanks below to show your results: Neutral atoms have the same number of protons and electrons. Positive ions have protons than electrons. Negative ions have protons than electrons. b) Develop a relationship (in the form of a single sentence or equation) that can predict the charge based on the number and types of particle. 6. Play with the simulation to discover what affects the mass number of your atom or ion. a) What is a rule for determining the mass number of an atom or ion? 7. Practice applying your understanding by playing 1 st and 2 nd levels on the game screen. Commented [TH2]: After a significant portion of the class has completed the first page, or once many of them are engaged with the Game, a class discussion around Part I is suggested. In the class discussion, focus particular attention on students answers to questions 5(b) and 6, which allow for a greater diversity of student thinking. BUILD AN ATOM 2

PART II: SYMBOL SCREEN 8. Using the Symbol readout box, figure out which particles affect each component of the atomic symbol. a) In the atomic symbol below, label each letter (a, b, c, and d) with: the particle(s) used to determine the letter, and how the value of each letter is determined. Commented [TH3]: Part II focuses primarily on student understanding and use of symbolic representations, specifically isotopic symbols. A facilitated discussion at the end of this section is advised, particularly if students share-out their definitions from question 9 and compare representations as a class. 9. Create a definition (using a complete sentence) for each of these items based on your labels from the atomic symbol above. a) Element Symbol b) Charge c) Atomic Number d) Mass Number d a b c 10. Practice applying your understanding by playing the 3 rd and 4 th game levels. Play until you can get all the questions correct on the 4 th level. 11. In addition to atomic symbol, we can represent atoms by name and mass number. a) Complete the table below: Symbol 12 6C +1 18 9 F 11 5 B Name Carbon-12 b) Each representation (Symbol and Name) in the table above provides information about the atom. Describe the similarities and differences between the Symbol and Name representations. BUILD AN ATOM 3

PART III: ISOTOPES 12. Play with the simulation to determine: a) Which particles affect the stability of the atom? b) Which particles do not affect the stability of the atom? Commented [YC4]: Part III of the activity extends the use of the sim representations to enable students to construct a definition of isotopes. 13. What are the names of the stable forms of oxygen? a) Oxygen-16 b) Oxygen- c) Oxygen- d) List all of the things that are the same about these atoms (ignore the electrons). e) List all of the things that are different about these atoms (ignore the electrons). 14. The atoms in the previous question are isotopes of each other. Based on this information, list the requirements for two atoms to be isotopes of each other. 15. Test your understanding of isotopes by examining the relationships between the pairs of atoms listed below: Atom 1 Atom 2 Relationship between atom 1 and atom 2 12 Isotopes Same Atom, Not Isotopes of Each Other 6C 13 6C Different Element Carbon-12 Argon-40 11 5 B An atom with 13 protons and 13 neutrons 12 6C Argon-41 Boron-10 An atom with 14 protons and 13 neutrons Isotopes Same Atom, Not Isotopes of Each Other Different Element Isotopes Same Atom, Not Isotopes of Each Other Different Element Isotopes Same Atom, Not Isotopes of Each Other Different Element Isotopes Same Atom, Not Isotopes of Each Other Different Element BUILD AN ATOM 4

70Ga +3 4 9 2 EXERCISES 16. The periodic table has a great deal of information about every atom. Using your periodic table, answer the following questions: a) What is the atomic number of chlorine (Cl)? Commented [TH5]: The exercises on this page may be best left as a homework assignment, as it is difficult to complete this in addition to the rest of the activity during class. Additionally, this section extends to elements outside of the scope of the simulation. b) What is the atomic number of tungsten (W)? c) How many protons are there in any Cl atom? d) How many protons are there in any Te atom? e) Can you tell from the periodic table exactly how many neutrons are in an atom? 17. Complete the following table: Atomic Mass Number of Number of Name Symbol Charge number Number neutrons Electrons hydrogen-2 2 H 1 2 1 1 0 3 H sodium-22 22 Na + 10 46 Ti -2 107Ag 19F -1 12 24 12 12 25 13 carbon-12 6 carbon-13 6 carbon-14 6 carbon-12 7 carbon-12 5 4 He 8 8 10 argon-40 18 18 70 Ga 7 8 8 18. To test your knowledge of isotopes, draw arrows between all pairs of atoms in the table above that are isotopes of each other. BUILD AN ATOM 5

BUILD AN ATOM PART I: ATOM SCREEN Build an Atom simulation (http://phet.colorado.edu/en/simulation/build-an-atom) 1. Explore the Build an Atom simulation with your group. As you explore, talk about what you find. 2. a) List two things your group observed in the simulation. b) What particle(s) are found in the center of the atom? 3. Play until you discover which particle(s) determine(s) the name of the element you build. What did you discover? 4. What is the name of the following atoms? a) An atom with 3 protons and 4 neutrons: b) An atom with 2 protons and 4 neutrons: c) An atom with 4 protons and 4 neutrons: 5. Play with the simulation to discover which particles affect the charge of an atom or ion. a) Fill in the blanks below to show your results: Neutral atoms have the same number of protons and electrons. Positive ions have protons than electrons. Negative ions have protons than electrons. b) Develop a relationship (in the form of a single sentence or equation) that can predict the charge based on the number and types of particle. 6. Play with the simulation to discover what affects the mass number of your atom or ion. a) What is a rule for determining the mass number of an atom or ion? 7. Practice applying your understanding by playing 1 st and 2 nd levels on the game screen. BUILD AN ATOM 1

PART II: SYMBOL SCREEN 8. Using the Symbol readout box, figure out which particles affect each component of the atomic symbol. a) In the atomic symbol below, label each letter (a, b, c, and d) with: the particle(s) used to determine the letter, and how the value of each letter is determined. 9. Create a definition (using a complete sentence) for each of these items based on your labels from the atomic symbol above. a) Element Symbol b) Charge c) Atomic Number d) Mass Number d a b c 10. Practice applying your understanding by playing the 3 rd and 4 th game levels. Play until you can get all the questions correct on the 4 th level. 11. In addition to atomic symbol, we can represent atoms by name and mass number. a) Complete the table below: Symbol 12 6C +1 18 9 F 11 5 B Name Carbon-12 b) Each representation (Symbol and Name) in the table above provides information about the atom. Describe the similarities and differences between the Symbol and Name representations. BUILD AN ATOM 2

PART III: ISOTOPES 12. Play with the simulation to determine: a) Which particles affect the stability of the atom? b) Which particles do not affect the stability of the atom? 13. What are the names of the stable forms of oxygen? a) Oxygen-16 b) Oxygen- c) Oxygen- d) List all of the things that are the same about these atoms (ignore the electrons). e) List all of the things that are different about these atoms (ignore the electrons). 14. The atoms in the previous question are isotopes of each other. Based on this information, list the requirements for two atoms to be isotopes of each other. 15. Test your understanding of isotopes by examining the relationships between the pairs of atoms listed below: Atom 1 Atom 2 Relationship between atom 1 and atom 2 12 Isotopes Same Atom, Not Isotopes of Each Other 6C 13 6C Different Element Carbon-12 Argon-40 11 5 B An atom with 13 protons and 13 neutrons 12 6C Argon-41 Boron-10 An atom with 14 protons and 13 neutrons Isotopes Same Atom, Not Isotopes of Each Other Different Element Isotopes Same Atom, Not Isotopes of Each Other Different Element Isotopes Same Atom, Not Isotopes of Each Other Different Element Isotopes Same Atom, Not Isotopes of Each Other Different Element BUILD AN ATOM 3

EXERCISES 16. The periodic table has a great deal of information about every atom. Using your periodic table, answer the following questions: a) What is the atomic number of chlorine (Cl)? b) What is the atomic number of tungsten (W)? c) How many protons are there in any Cl atom? d) How many protons are there in any Te atom? e) Can you tell from the periodic table exactly how many neutrons are in an atom? 17. Complete the following table: Name Symbol Atomic number Mass Number Number of neutrons Number of Electrons hydrogen-2 2 H 1 2 1 1 0 3 H sodium-22 22 Na + 10 46 Ti -2 107 Ag 19 F -1 12 24 12 12 25 13 carbon-12 6 carbon-13 6 carbon-14 6 carbon-12 7 carbon-12 5 4 He 8 8 10 argon-40 18 18 70 Ga Charge 70 Ga +3 4 9 2 7 8 8 18. To test your knowledge of isotopes, draw arrows between all pairs of atoms in the table above that are isotopes of each other. BUILD AN ATOM 4

Clicker Questions for Build an Atom AUTHORS: Yuen-ying Carpenter (University of Colorado Boulder) Trish Loeblein (University of Colorado Boulder) Robert Parson (University of Colorado Boulder) COURSE: Introductory / Preparatory College Chemistry COPYRIGHT: This work is licensed under a Creative Commons Attribution 4.0 International License.

If you have 5 protons and 6 neutrons, how many electrons would you add to make a neutral atom? a. 5 electrons b. 6 electrons c. 11 electrons

If you have an atom with 8 protons, 9 neutrons and 10 electrons, what is its mass number? a. Zero b. 8 c. 16 d. 17 e. 25?

For the same atom, with 8 protons, 9 neutrons and 10 electrons, what type of atom or ion is it? a. Neutral atom b. +2 ion c. +1 ion d. -1 ion e. -2 ion

If you have 5 protons, 6 neutrons, & 5 electrons, what would the symbol look like? A B C D

Start atom Remove Final atom Which statement is FALSE about the final atom? a. It is a different element than the start atom. b. It has 4 neutrons less than the start atom. c. It has 2 protons less than the start atom. d. None of the above.

What is the correct symbol for an isotope of carbon with 7 neutrons? 7 a. 6C 13 b. 7 C 6 c. 13C 13 d. 6 C

What is the correct identity of an element with the following isotopic symbol and how many neutrons does it have? 79 35 X a. Gold, 114 neutrons b. Bromine, 44 neutrons c. Gold, 44 neutrons d. Bromine, 114 neutrons

Which are isotopes? I II a. I and II b. II and III c. I and III d. I, II and III III

Which of these pairs of atoms are isotopes? Pair A Pair B Pair C # of protons 6 8 5 2 12 12 # of neutrons 8 8 5 3 13 14

Which of these is not an isotope of 14 C? 6 a. An atom with 6 protons and 7 neutrons. b. The atom 12 C 6 c. An atom with 8 protons and 6 neutrons. d. The ion 13 C +2 6

Suppose you built a scale model of the atom the same width as a football field (100 m). What could you use to represent the nucleus in your model? A. A marble (1 cm) B. A golf ball (4 cm) C. A soccer ball (20 cm) D. A yoga/exercise ball (50 cm)

Clicker Questions for Isotopes and Atomic Mass AUTHORS: Yuen-ying Carpenter (University of Colorado Boulder) Robert Parson (University of Colorado Boulder) Trish Loeblein (University of Colorado Boulder) COURSE: Introductory Chemistry COPYRIGHT: This work is licensed under a Creative Commons Attribution 4.0 International License.

a. Carbon-12 b. Carbon-14 c. Oxygen-14 d. More than one of these What would this be?

Reason: The number of protons tells the name of the atom; the mass is given by the sum of protons and neutrons 6 protons +8 neutrons

Which of these pairs of atoms are isotopes? Pair A Pair B Pair C # of protons 6 8 5 2 12 12 # of neutrons 8 8 5 3 12 14

What is the approximate average mass of a hydrogen atom in this sample? a. 6 amu b. 2 amu c. 1.5 amu d. 1 amu

Reason: 3/6 gives 50% of each, so 0.5*2 + 0.5*1 = 1.5 amu or 3*2 + 2*1 = 1.5 amu Why are there more digits in the answer in the sim?

What is the approximate average mass of an argon atom in this sample? a. 40 amu b. 38 amu c. 37.5 amu

Calculation: 0.5*36 + 0.25*38 + 0.25*40 = 37.5 amu

Mass of 1 atom = 6.01512 amu Mass of 1 atom = 7.01600 amu 6.41548 Is the average atomic mass closer to the mass of a lithium-6 atom or a lithium-7 atom? a. Lithium-6 b. Lithium-7

To figure this out, let s start with some small samples Mass of 1 atom = 6.01512 amu Mass of 1 atom = 7.01600 amu 6.41548? Will the average atomic mass of sample 2 be a. More than Sample 1 b. Same as Sample 1 c. Less than Sample 1 d. I don t know how to determine this.

Sample 2 Equal to Sample 1 6.41548 amu average Equal to Sample 1 6.41548 amu average

In nature, chlorine has the following composition: The average atomic mass of a natural sample of chlorine is a Between 35-36 amu b About 36 amu c Between 36-37 amu

Neon has three naturally occurring isotopes: 20 Ne 19.992 amu 21 Ne 20.994 amu 22 Ne 21.991 amu 10 Ne 20.18 Which isotope has the highest natural abundance? a. 20 Ne b. 21 Ne c. 22 Ne d. All isotopes have the same abundance e. Impossible to tell from this information

Magnesium has three naturally occurring isotopes: 24 Mg 23.985 amu 25 Mg 24.986 amu 26 Mg 25.983 amu In a sample with an average atomic mass of 24.98 amu, which isotope is the most abundant? a. 24 Mg b. 25 Mg c. 26 Mg d. All isotopes have the same abundance e. Impossible to tell from this information

Neon has three naturally occurring isotopes: 20 Ne 21 Ne 10 Ne 20.18 22 Ne Which isotope has the highest natural abundance? Can we answer the question without being given the exact isotopic masses? a. Yes b. No

Neon has three naturally occurring isotopes: 20 Ne 21 Ne 22 Ne Which isotope has the highest abundance in a sample of Ne? Can we answer the question without being given the average atomic mass of the sample? a. Yes b. No

Neon has three naturally occurring isotopes: 20 Ne 21 Ne 22 Ne Which isotope has the highest abundance in a sample of Ne with average atomic mass of? Can we answer the question for any sample, no matter what the average atomic mass? a. Yes b. No

Challenge problem: Argon has three stable isotopes, with these atomic masses: 36 Ar 35.968 amu 38 Ar 37.963 amu 40 Ar 39.962 amu You measure the average atomic mass of several different samples of argon, and are asked to predict the most abundant isotope in each sample. For which of these samples is this prediction impossible? Sample A, a naturally-occurring sample of argon Sample B, average atomic mass = 36.5 amu Sample C, average atomic mass = 37.5 amu Sample D, average atomic mass = 39.5 amu

Lithium 3 Li 6.941 Complete the following sentence with a unit. On average, lithium weighs 6.941. a. g / atom b. g / mol c. amu / mol d. amu / atom e. More than one of the above

TITLE Isotopes and Atomic Mass AUTHORS Timothy Herzog (Weber State University) COURSE General Chemistry I TYPE In-Class Guided-Inquiry Activity TEACHING MODE Facilitated Group Inquiry LEARNING GOALS Students will be able to: Explain the difference between atomic mass and mass number Calculate average atomic mass from percent abundance and isotopic mass. COPYRIGHT This work is licensed under a Creative Commons Attribution 4.0 International License. This license allows users to share and adapt the materials, as long as appropriate attribution is given (with a link to the original), an indication if changes have been made, and an indication of the original licensing. ISOTOPES AND ATMOIC MASS 1

ISOTOPES AND ATOMIC MASS MODEL 1: Make Isotopes Commented [YC1]: Learning goals: Explain the difference between atomic mass and mass number Calculate average atomic mass from percent abundance and isotopic mass. Open the Isotopes and Atomic Mass simulation http://phet.colorado.edu/en/simulation/isotopes-and-atomic-mass Play with the Make Isotopes tab of the simulation for a few minutes and then answer the following questions. 1. What particles determine the mass number? 2. Why is mass number always a whole number? 3. One isotope of carbon (C) has exactly the same mass number and atomic mass since it was used as the definition of the atomic mass unit (amu). Which isotope is it and what is its atomic mass? 4. What is the approximate mass of one proton? amu 5. What is the approximate mass of one neutron? amu 6. Look at 3 or 4 other atoms using the simulation. Do any of them have a whole number for atomic mass? MODEL 2: Mix Isotopes Commented [TH2]: Facilitation tip: This is a good time to stop and briefly discuss mass defect and possible E=mc 2 and to reinforce the reasons why 12 C has the only exact mass. Play with the Mix Isotopes tab for a few minutes, then answer the following questions. 1. What are the factors that affect the average atomic mass of a mixture of isotopes? 2. Beryllium (Be) and Fluorine (F) have only one stable isotope. Use the sim and the periodic table to complete the following table: Element Mass of 1 atom Average mass of 2 Average mass of 3 Atomic mass atoms (sim) atoms (sim) (periodic table) Beryllium 9.01218 amu (Be) Fluorine (F) 18.99840 amu 3. Why are all the values in each row of the table above the same? ISOTOPES AND ATOMIC MASS 2

4. Lithium has only two stable isotopes. Use the sim to determine the following: a. Atomic mass of lithium-6 = amu b. Atomic mass of lithium-7 = amu c. Average atomic mass of a sample containing three lithium-6 atoms and two lithium-7 atoms. amu d. Is the average atomic mass you just determined closer to the mass of lithium-6 or lithium-7? Explain 5. Describe a method to calculate the average atomic mass of the sample in the previous question using only the atomic masses of lithium-6 and lithium-7 without using the simulation. Commented [YC3]: Facilitation tip: Questions 5-6 in this section focus on the calculation of average atomic mass using the number of atoms of each isotope, which is typically easier for students than the calculation of average atomic mass from percent abundance. We extend this calculation to the use of percent abundances in the next section, Nature s Mix of Isotopes 6. Test your method by creating a few sample mixtures of isotopes with the sim and see if your method correctly predicts the average atomic mass of that sample from only the atomic masses of the isotopes and the quantity of each isotope. Use the table below to track your progress. Element Atomic mass and quantity of each isotope Average atomic mass of sample (calculate yourself) Average atomic mass of sample (from simulation) MODEL 3: Nature s mix of isotopes 1. Using the sim, examine Nature s mix of isotopes for several different elements. If you assumed 100 total atoms in a sample, how could you relate the % values shown in the sim into a number you could use for your calculation of average atomic mass? ISOTOPES AND ATOMIC MASS 3

2. Calculate the atomic mass of each of the following elements using your method from above. Test your answer using the Nature s mix of isotopes and the periodic table. Keep going until you can get two in a row right. Element Isotope 1 Isotope 2 Isotope 3 Mass (amu) %age Mass (amu) %age Mass (amu) %age Calculated average atomic mass (amu) Check answer with sim Yes No Hydrogen 1.007 99.98 2.01410 0.011 - - Silicon 27.97 92.22 28.9764 4.685 29.97377 3.092 Nitrogen 14.00 99.63 15.0001 0.364 - - Argon 35.96 0.336 37.9627 0.063 39.96238 99.60 Calculations / Rough work: ISOTOPES AND ATOMIC MASS 4

EXERCISES 1. Titanium has five common isotopes: 46 Ti (8.00%), mass= 45.953 amu 47 Ti (7.80%), mass= 46.952 amu 48 Ti (73.40%), mass= 47.947 amu 49 Ti (5.50%), mass= 48.948 amu 50 Ti (5.30%), mass = 49.945 amu Calculate the average atomic mass of titanium. Commented [TH4]: These exercises could be left for takehome practice, as they focus primarily on computational skill, not conceptual understanding. 2. The atomic mass of boron is 10.81 amu. Boron has two isotopes: Boron-10 has a mass of 10.01 amu. Boron-11 has a mass of 11.01 amu. What is the %age of each isotope in boron? (check your answer with the simulation) 3. A certain sample of rubidium has just two isotopes, 85 Rb (mass = 84.911amu) and 87 Rb (mass = 86.909amu). The atomic mass of this sample is 86.231 amu. What are the percentages of the isotopes in this sample? ISOTOPES AND ATOMIC MASS 5

ISOTOPES AND ATOMIC MASS MODEL 1: Make Isotopes Open the Isotopes and Atomic Mass simulation http://phet.colorado.edu/en/simulation/isotopes-and-atomic-mass Play with the Make Isotopes tab of the simulation for a few minutes and then answer the following questions. 1. What particles determine the mass number? 2. Why is mass number always a whole number? 3. One isotope of carbon (C) has exactly the same mass number and atomic mass since it was used as the definition of the atomic mass unit (amu). Which isotope is it and what is its atomic mass? 4. What is the approximate mass of one proton? amu 5. What is the approximate mass of one neutron? amu 6. Look at 3 or 4 other atoms using the simulation. Do any of them have a whole number for atomic mass? MODEL 2: Mix Isotopes Play with the Mix Isotopes tab for a few minutes, then answer the following questions. 1. What are the factors that affect the average atomic mass of a mixture of isotopes? 2. Beryllium (Be) and Fluorine (F) have only one stable isotope. Use the sim and the periodic table to complete the following table: Element Mass of 1 atom Average mass of 2 Average mass of 3 Atomic mass atoms (sim) atoms (sim) (periodic table) Beryllium 9.01218 amu (Be) Fluorine (F) 18.99840 amu 3. Why are all the values in each row of the table above the same? ISOTOPES AND ATMOIC MASS 1

4. Lithium has only two stable isotopes. Use the sim to determine the following: a. Atomic mass of lithium-6 = amu b. Atomic mass of lithium-7 = amu c. Average atomic mass of a sample containing three lithium-6 atoms and two lithium-7 atoms. amu d. Is the average atomic mass you just determined closer to the mass of lithium-6 or lithium-7? Explain 5. Describe a method to calculate the average atomic mass of the sample in the previous question using only the atomic masses of lithium-6 and lithium-7 without using the simulation. 6. Test your method by creating a few sample mixtures of isotopes with the sim and see if your method correctly predicts the average atomic mass of that sample from only the atomic masses of the isotopes and the quantity of each isotope. Use the table below to track your progress. Element Atomic mass and quantity of each isotope Average atomic mass of sample (calculate yourself) Average atomic mass of sample (from simulation) MODEL 3: Nature s mix of isotopes 1. Using the sim, examine Nature s mix of isotopes for several different elements. If you assumed 100 total atoms in a sample, how could you relate the % values shown in the sim into a number you could use for your calculation of average atomic mass? ISOTOPES AND ATOMIC MASS 2

2. Calculate the atomic mass of each of the following elements using your method from above. Test your answer using the Nature s mix of isotopes and the periodic table. Keep going until you can get two in a row right. Element Isotope 1 Isotope 2 Isotope 3 Mass (amu) %age Mass (amu) %age Mass (amu) %age Calculated average atomic mass (amu) Check answer with sim Yes No Hydrogen 1.007 99.98 2.01410 0.011 - - Silicon 27.97 92.22 28.9764 4.685 29.97377 3.092 Nitrogen 14.00 99.63 15.0001 0.364 - - Argon 35.96 0.336 37.9627 0.063 39.96238 99.60 Calculations / Rough work: ISOTOPES AND ATOMIC MASS 3

EXERCISES 1. Titanium has five common isotopes: 46 Ti (8.00%), mass= 45.953 amu 47 Ti (7.80%), mass= 46.952 amu 48 Ti (73.40%), mass= 47.947 amu 49 Ti (5.50%), mass= 48.948 amu 50 Ti (5.30%), mass = 49.945 amu Calculate the average atomic mass of titanium. 2. The atomic mass of boron is 10.81 amu. Boron has two isotopes: Boron-10 has a mass of 10.01 amu. Boron-11 has a mass of 11.01 amu. What is the %age of each isotope in boron? (check your answer with the simulation) 3. A certain sample of rubidium has just two isotopes, 85 Rb (mass = 84.911amu) and 87 Rb (mass = 86.909amu). The atomic mass of this sample is 86.231 amu. What are the percentages of the isotopes in this sample? ISOTOPES AND ATOMIC MASS 4

Unit 2 Atomic Structure Big Idea: Atomic structure explains patterns in the behavior of elements and allows us to predict the chemical and physical behavior of a given element. The organization of elements on the periodic table reflects trends in both atomic structure and element properties. Essential Questions: 1) How do we know what an atom looks like if we can t see atoms? 2) Why are silver and gold used to make jewelry? 3) Why are chlorine and iodine used as disinfectants? 4) Why do we use helium to inflate balloons instead of hydrogen? Colorado Academic Standard: SC09-GR.HS-S.1-GLE.2 Matter has definite structure that determines characteristic physical and chemical properties. Evidence Outcomes: a) Develop, communicate, and justify an evidence-based scientific explanation supporting the current model of an atom. b) Use characteristic physical and chemical properties to develop predictions and supporting claims about elements positions on the periodic table. NGSS: Structure and Properties of Matter Performance Expectation: HS-PS1-1 Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms. Disciplinary Core Ideas: PS1.A: Structure and Properties of Matter Each atom has a charges substructure consisting of a nucleus, which is made of protons and neutrons, surrounded by electrons. The periodic table orders elements horizontally by the number of protons in the atom s nucleus and places those with similar chemical properties in columns. The repeating patterns of this table reflect patters of outer electron states. PS2.B: Types of Interactions Attraction and repulsion between electric charges at the atomic scale explain the structure, properties, and transformations of matter, as well as the contact forces between material objects. Science and Engineering Practices: Developing and Using Models Use a model to predict the relationships between systems or between components of a system. Crosscutting Concepts: Patterns Different patterns may be observed at each of the scales at which a system is studied and can provide evidence for causality in explanations of phenomena. Hanson, A.J. 2015 1

Motion and Stability: Forces and Interactions Performance Expectation: HS-PS2-4 Use mathematical representations of Newton s Law of Gravitation and Coulomb s Law to describe and predict the gravitational and electrostatic forces between objects. Disciplinary Core Ideas: PS2.B Types of Interactions Newton s law of universal gravitation and Coulomb s law provide the mathematical models to describe and predict the effects of gravitational and electrostatic forces between distant objects. Forces at a distance are explained by fields (gravitational, electric, and magnetic) permeating space that can transfer energy through space. Magnets or electric currents cause magnetic fields; electric charges or changing magnetic fields cause electric fields. Science and Engineering Practices: Using Mathematics and Computational Thinking Use mathematical representations of phenomena to describe explanations. Crosscutting Concepts: Patterns Different patterns may be observed at each of the scales at which a system is studied and can provide evidence for causality in explanations of phenomena. Waves and Electromagnetic Radiation Performance Expectation: HS-PS4-1 Use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling in various media. Disciplinary Core Ideas: PS4.A: Wave Properties The wavelength and frequency of a wave are related to one another by the speed of travel of the wave, which depends on the type of wave and the medium through which it is passing. Science and Engineering Practices: Using Mathematics and Computational Thinking Use mathematical representations of phenomena or design solutions to describe and/or support claims and/or explanations. Crosscutting Concepts: Cause and Effect Empirical evidence is required to differentiate between cause and correlations and make claims about specific causes and effects. Performance Expectation: HS-PS4-3 Evaluate the claims, evidence, and reasoning behind the idea that electromagnetic radiation can be described either by a wave model or a particle model, and that for some situations one model is more useful than the other. Disciplinary Core Ideas: PS4.B: Electromagnetic Radiation Electromagnetic radiation (e.g., radio, microwaves, light) can be modeled as a wave of changing electric and magnetic fields or as particles called photons. The wave model is useful for explaining many features of electromagnetic radiation, and the particle model explains other features. Hanson, A.J. 2015 2

Science and Engineering Practices: Engaging in Argument from Evidence Evaluate the claims, evidence and reasoning behind currently accepted explanations or solutions to determine the merits of arguments. Crosscutting Concepts: Systems and System Models Models (e.g., physical, mathematical, computer models) can be used to simulate systems and interactions-including energy, matter, and information flows-within and between systems at different scales. Lesson In Class Activity Number 1 Question of the day: What does an atom look like? Activities: Groups draw pictures or make models to show the basic structure of an atom. Drawings/models should show location of protons, neutrons, and electrons, but do not need to be to scale. Law of Definite Proportions Lab Activity Mg (s) + Cu(C2H3O2)2 (aq) 2 Question of the day: What does an atom look like? Activities: Model of the Atom Take 1 (groups use lab data ONLY to propose a model of an atom) Class discussion/clicker questions for about Law of Definite Proportions Dalton s atomic theory Learning Objectives Students will be able to: Describe what an atom looks like using background knowledge from previous science classes. Experimentally determine the mass ratio of Mg and Cu in a chemical reaction. Relate the experimentally determined mass ratio of magnesium to copper to the Law of Definite Proportions. Relate the experimentally determined mass ratio of magnesium to copper to the Law of Definite Proportions. Explain the major postulates of Dalton s atomic theory. Develop an atomic model based on experimental evidence obtained in class from the reaction between Mg and copper (II) acetate. Compare student generated models of the atom with Dalton s atomic theory/model. Homework Calculate the mass ratio of Mg to Cu using experimental data. Rough draft of atomic model using evidence collected in lab activity. Writing assignment: Using the Law of Definite Proportions and your experimental data, justify the atomic model you created with your group in class. Compare and contrast your model to the atomic model proposed by Dalton. Hanson, A.J. 2015 3

Lesson Number In Class Activity 3 Question of the day: What does an atom look like? How did we discover electrons and protons? Activities: Thomson s cathode ray experiment demonstration Model of the Atom Take 2 Battleship game modeling Rutherford s gold foil experiment Rutherford scattering PhET simulation Model of the Atom Take 3 4 Question of the day: What does an atom look like? Where are electrons found in an atom? What evidence do we have to support this idea? Activities: View hydrogen spectrum Electron Energy and Light POGIL activity Model of the Atom Take 4 Learning Objectives Students will be able to: Describe J.J. Thomson s experiment with cathode ray tubes and the evidence he collected about atomic structure. Analyze the billiard ball model of the atom using the results of Thomson s cathode ray tube experiment. Propose an atomic model that uses Thomson s data from the cathode ray tube experiment. Describe the experiment Rutherford used to test Thomson s atomic model. Analyze the plum pudding model of the atom using the results of Rutherford s gold foil experiment. Propose an atomic model that uses Rutherford s data from the gold foil experiment. Explain the experimental evidence Rutherford used to propose the nuclear model of the atom. Compare and contrast the plum pudding and nuclear models of an atom. Compare the plum pudding and nuclear atomic models to student generated models of the atom. Describe what you see when electricity is passed through a glass tube containing hydrogen gas. Define quantum and explain what it means for energy to be quantized. Analyze the nuclear model of the atom using evidence from Bohr s experiments. Explain where Bohr thought electrons were located in an atom. Describe the experimental evidence that Bohr used to develop his atomic model. Compare the Bohr model of the atom to student generated models of the atom. Homework Writing assignment: Compare and contrast the Billiard Ball, Plum Pudding, and Nuclear Models of the atom. Cite experimental evidence used to develop each model. State reasons the model was revised. Writing assignment: Compare and contrast the Bohr model of the atom to previous atomic models. Cite experimental evidence used to develop each model. State reasons the model was revised. Hanson, A.J. 2015 4

Lesson Number In Class Activity 5 Question of the day: What does an atom look like? Where are electrons found in an atom? What evidence do we have to support this idea? Activities: Energy, frequency, wavelength calculations Flame test lab 6 Question of the day: How do we know the number of protons, neutrons, and electrons in an atom? How can we calculate the mass number of an atom? Activities: Build an Atom PhET Simulation 7 Question of the day: Are all atoms of the same element identical? Activities: Isotopes and Atomic Mass PhET simulation 8 Question of the day: How is atomic mass calculated? Activities: Average mass of Candium or Beanium Calculating average atomic mass of elements Learning Objectives Students will be able to: Calculate the wavelength, frequency, or energy of electromagnetic radiation. Explain what causes different colors of light in a fireworks show. Describe how the emission spectrum of an element is related to its electron arrangement. Describe the charge, mass, and location of protons, neutrons and electrons in an atom. Write and interpret atomic symbols. Calculate the mass number of an atom. Determine the number of protons, neutrons, and electrons in a neutral atom. Define the term isotope. Identify atoms that represent two different isotopes of the same element. Describe factors that make an atom stable or unstable. Develop a procedure to determine the average atomic mass of an element. Develop and carry out a procedure to determine the average mass of a sample of beans or candy. Explain the difference between an average and a weighted average. Write and carry out a procedure to calculate the average atomic mass of an element. Homework Wavelength, Energy, Frequency Practice sheet Complete all 4 levels of the game in Build an Atom. Screenshot your results and submit on Edmodo. Write a procedure to determine the average atomic mass of an element. Isotopes and Atomic Mass Practice Sheet Hanson, A.J. 2015 5

Lesson In Class Activity Number 9 Question of the day: What does an atom look like? What is incorrect about the Bohr model of the atom? What evidence do we have to support this idea? Activities: View neon and argon emission spectrum. Models of the Hydrogen Atom PhET simulation (demonstration) Electron Configuration POGIL activity Model of the Atom Take 5 10 Question of the day: Why doesn t the periodic table list elements in alphabetical order? Activities: Cracking the Periodic Table Code POGIL Practice electron configurations 11 Question of the day: Why doesn t the periodic table list elements in alphabetical order? Activities: Valence Electron Ion formation Build an Atom PhET Simulation revisited 12 Question of the day: How was the first periodic table constructed? What is periodic about the periodic table? Hanson, A.J. 2015 Activities: Alien card sort What was Mendeleev Thinking? Learning Objectives Students will be able to: Describe what you see when electricity is passed through a glass tube containing neon or argon gas. Analyze the Bohr model of the atom using evidence from the neon and argon emission spectra. Propose a new atomic model to account for data that does not fit the Bohr model. Write an electron configuration for any element in the first four periods on the periodic table. Explain how the periodic table can be used to determine the electron configuration of an atom of any element on the periodic table. Use the periodic table to predict where the last electrons are located in an atom of any element listed on the periodic table. Identify the valance electrons in an atom using the electron configuration. Relate the number of valence electrons to an element s location on the periodic table. Calculate the charge, mass, and number of protons, neutrons, and electrons in an ion. Explain how the first periodic table of the elements was created. Homework Writing assignment: Explain why the Bohr model of the atom needed to be revised. Cite experimental evidence that was used to support the idea that Bohr s model needed to be revised. Writing assignment: Compare and contrast the quantum mechanical model of the atom to previous atomic models. Cite experimental evidence used to develop the quantum mechanical model. Valence Electrons and Ions Practice Sheet Reading assignment: Creating the First Periodic Table 6

Lesson In Class Activity Number 13 Question of the day: What types of attraction occur between the nucleus and the electrons? Activities: Coulombic Attraction POGIL Activity 14 Question of the day: What is periodic about the periodic table? What patterns exist on the periodic table? Activities: Mini-lab: Properties of Elements Periodic Trends POGIL activity or Graphing Periodic Trends activity 15 Assessments RAFT Assignment: Choose one of the following essential questions for this chapter to complete your RAFT assignment: How do we know what an atom looks like if we can t see atoms? Why are silver and gold used to make jewelry? Why are chlorine and iodine used as disinfectants? Why do we use helium to inflate balloons instead of hydrogen? Learning Objectives Students will be able to: Explain the factors that influence the strength of the electrostatic attraction between oppositely charged particles. List the properties of metals, nonmetals, and metalloids. Classify an element based on its properties. Relate the location and atomic structure of an element to its physical properties. Analyze the trends in atomic radius, first ionization energy, and electronegativity on the periodic table. Justify the trends in atomic radius, first ionization energy, and electronegativity using your knowledge of atomic structure. Given a list of elements, place the elements in order of increasing or decreasing atomic radius, first ionization energy, or electronegativity. Justify your reasoning. Homework Coulombic Attraction Practice sheet Writing assignment: Periodic Trends Atomic Radius, Ionization Energy, and Electronegativity RAFT assignment Study for Unit 2 test. Hanson, A.J. 2015 7