Atom Building Game. Investigations. 4 Investigations 4 Blackline Masters 4 Assessment Questions

Transcription

1 Atom Building Game Investigations 4 Investigations 4 Blackline Masters 4 Assessment Questions St r u c t u re of the Atom

2 How to Use the Three Levels of Investigations This Curriculum Resource Guide has been designed with three ability levels. Level A Investigations are introductory in nature and contain little or no math. Investigations in Level A cover one or two basic concepts and can be accomplished in one or two classroom periods. Level B investigations are for intermediate students in an introductory class at high school or advanced middle school group. Students will need a basic level of math knowledge for this level. Level C investigations are for students with advanced math skills and prior science knowledge. Depending on the student math background, Level B and Level C investigations present a progression from basic observation to complex analysis. The three levels of investigations can effectively be used in different ways. The levels allow a greater flexibility when matching instructional needs with student abilities. Below are suggestions for how to use the levels in your classroom. Multiple-level learning Multiple level learning works between grades but also within a single grade/classroom. In today's classroom, heterogeneous ability grouping is the norm. To meet the ability needs of the students, you can choose different investigations. For example, you teach a ninth grade class. The majority of the students are on grade level but the class also is comprised of English language learners and students who need extra help. You start all the students by teaching how the equipment works. You then divide your 9th grade class into groups by their science background and ability level. You decide that two groups should start with Level A investigations while the majority of the class begins with Level B. You have three students who are far ahead in science and very motivated. You start with the third investigation in Level B and then give them Level C. All students are using the same equipment so discussion can center on the equipment and basic principles. Teaching to the needs of English language learners You want your students to have the same instruction as the students in their grade level. The vocabulary proves too difficult and the pace of the instruction in the regular classroom too fast. You obtain the Atom Building Game sets before students begin the instruction to give students extra time with the equipment. When the students are comfortable with the equipment it will be easier to do learn the science. You use level A investigations because the investigations are basic in nature and the students can work with the vocabulary and learn procedures.

3 Contents Atom Building Game Investigations Level A Investigations A-1 Building Atoms Key Question: What is an atom? By using the Atom Building Game to build atoms, students learn about the parts of the atom and the periodic table of the elements. Students use atomic number and mass number to calculate the charge on an atom and figure out the number of protons, neutrons, and electrons in an atom. Students learn the terms ion and isotope. A-2 Atomic Challenge Key Question: What holds an atom together? In this investigation, students learn about the atomic forces that hold an atom together. Students also learn what it means when an atom is stable and neutral. Using their understanding of atomic structure, students play a game called Atomic Challenge using the Atom Building Game. A-3 Building Molecules Key Question: What is a molecule? Students learn about the role of energy levels in the bonding of atoms by building atoms using the Atom Building Game. From their work, students figure out rules for how atoms form chemical bonds. Students learn the difference between compounds and elements and how to write simple molecular formulas. Students use their understanding of these concepts to model the formation of a water molecule. Level B Investigations B-1 Nuclear Reactions Key Question: How are elements organized on the periodic table? Students discover how atomic structure is related to the placement of elements on the periodic table. and use their knowledge to play a game called Nuclear Reactions. By playing this game, students simulate nuclear reactions. Students learn the difference between fusion and fission, and the meaning of the term radioactivity. B-2 Bonding and Molecules Key Question: Why do atoms form chemical bonds? In this investigation, students apply their understanding of the fundamentals of atomic structure to figure out why elements combine to form compounds. Students learn that electrons in the outermost energy level of an atom, the valence electrons, are important in the formation of a chemical bond between atoms. They learn that the oxidation number of an atom is helpful in determining the number of electrons an atom contributes during bond formation. i

4 Level C Investigations C-1 Electrons and the Periodic Table Key Question: How is the periodic table organized? In this investigation, students learn that the placement of atoms on the periodic table is based on atomic structure. Students use the Atom Building Game to discover the arrangement of electrons around the nucleus. They learn about electron orbitals and electron configuration. C-2 Energy and the Quantum Theory Key Question: How do atoms make light? In this investigation, students learn how light is absorbed and emitted from atoms. Students play Photons and Lasers, a game that uses the Atom Building Game board. In the game, students model how electrons are excited to move to higher energy levels, and how electrons drop back to the ground state and release light. C-3 Valence Electrons and Molecules Key Question: What is the role of electrons in forming molecules? In this investigation, students discover why atoms form bonds. Through inquiry they derive rules, such as the octet rule, for predicting which atoms form molecules. They learn the role of valence electrons and oxidation numbers in forming molecules, and learn how to write molecular formulas. They model the formation of molecules using the Atom Building Game. At the end of the investigation, students work through an exercise that illustrates how average atomic mass is related to the mass numbers and abundance of isotopes in nature. ii

5 A1 Building Atoms What is an atom? Atoms make up everything you see, touch, smell, and eat. Atoms are so small you can t see them. It takes millions and millions of atoms to form a single crystal of salt in your salt shaker. Each type of atom is called an element. All the elements are represented on a special chart called the periodic table. In this investigation, you will use the Atom Building Game to learn the parts of an atom and what makes the atoms of one element different from the atoms of another element. A What are the parts of an atom? The Atom Building Game represents a model of an atom. The center of the board represents the nucleus of an atom. The outer rings around the center represent energy levels. Three colors of marbles come with the game. The marbles represent the three kinds of subatomic particles in the atom. The green marbles represent protons. The blue marbles represent neutrons. Protons and neutrons always go in the nucleus of an atom. The yellow marbles represent electrons. Electrons always go in the energy levels. Investigation A1 Protons and electrons have charge. Charge can be positive or negative. Each proton has a positive charge of +1. Each electron has a negative charge of 1. Neutrons have no charge and are neutral. When the number of protons equals the number of electrons in an atom, the atom has no charge. An atom has a charge when the number of protons is different from the number of electrons. An atom with a positive or negative charge is called an ion. As you answer the questions, you will build a beryllium atom. When asked to find the total charge for a group of subatomic particles, use the following formula: Number of particles Charge of one particle = Total charge Materials One Atom Building Game with marbles. Periodic table that comes with the game a. Place four protons (green marbles) in the center of the board. What is the total charge of the protons? b. Place five neutrons (blue marbles) in the center of the board with the protons. What is the total charge of the protons plus the neutrons? Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 1

6 c. If you have four electrons (yellow marbles), what is the total charge of these particles? d. Finish building the atom, by adding the four electrons to the outer levels on the board. Now, add the total charges of all the particles in the atom. What is the total charge of the atom you built? e. Draw a diagram of the beryllium atom. Include all the parts of the atom. Label your diagram. 2 Copyright 2009 CPO Science Can be duplicated for classroom use

7 B Identifying elements Investigation A1 On the Atom Building Game board, you have a model of a beryllium atom. This atom has four protons, five neutrons, and four electrons. You can find out more information about beryllium by looking at the periodic table that comes with the Atom Building Game. a. What is the symbol for the element beryllium? b. What is the atomic number for beryllium? The atomic number of an element is equal to the number of protons in the nucleus of an atom of the element. Since the atomic number of beryllium is 4, all beryllium atoms have 4 protons. Fill in the Element Name and Atomic Number columns in the table below. Element Name Atomic Number Number of protons Number of electrons Mass number Number of neutrons Hydrogen 1 Oxygen Calcium C Building atoms 1. Use the atomic numbers for the elements to fill in the Number of protons column in the table above. 2. The number of electrons in an atom equals the number of protons. Use this information to fill in the Number of electrons column in table above. Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 3

8 D 3. The mass number for an atom is equal to the number of protons and neutrons in the nucleus. Atoms of an element can have different numbers of neutrons, but all atoms of an element have the same number of protons. The formula for mass number is: Number of protons 4. Rearrange the formula for mass number so that it is a formula for figuring out the number of neutrons in an atom. Use this new formula and the mass numbers in the table above to fill in the Number of neutrons column. What are isotopes? + Number of neutrons = Mass number Atoms of the same element that have different mass numbers are called isotopes. Hydrogen has two isotopes. One has a mass number of 1 and is called hydrogen-1. The other has a mass number of 2 and is called hydrogen-2. a. How many neutrons does hydrogen-1 have? How many neutrons does hydrogen-2 have? b. How many isotopes does magnesium have? Write the names of these isotopes. c. How many neutrons does an atom of copper-65 have? How many protons does it have? 4 Copyright 2009 CPO Science Can be duplicated for classroom use

9 Assessment Investigation A1 1. Use the periodic table to fill the Atomic number and Number of protons columns for each atom in the table. Use the numbers of protons and electrons to fill in the Total charge column. Then decide whether each atom is an ion. Element name Atomic number Number of protons Number of electrons Total charge Is the atom an ion? hydrogen 0 lithium 2 beryllium 4 boron 2 oxygen 8 fluorine The first two columns of the table below are partially filled in. Use the periodic table to help you fill in the other columns. Then fill in the Number of protons and Number of electrons. Use the mass number and number of protons to fill in the Number of neutrons column for each atom. Element name Atomic number Number of protons Number of electrons Mass number Number of neutrons hydrogen oxygen silicon 28 phosphorus xenon 124 Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 5

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11 A2 Atomic Challenge What holds and atom together? An atom s structure includes a nucleus with protons and neutrons, and energy levels with electrons. Each of the protons has a positive charge. Each of the electrons has a negative charge. Positive charges and negative charges attract one another. The attractive atomic force between charges helps hold an atom together. In this investigation, you will learn more about the forces that hold an atom together. You will use your understanding of atomic structure to play a game called the Atomic Challenge. A What holds an atom together? Investigation A2 One of the atomic forces that holds an atom together is called electromagnetic force. This force follows certain rules. The rules are explained below and illustrated in the diagram. The rules for electromagnetic force are: Positive charges attract negative charges. Positive charges repel other positive charges. Negative charges repel other negative charges. Electromagnetic force is responsible for holding the electrons in place. The electrons are attracted to the protons in the nucleus of the atom. Materials One Atom Building Game with marbles. Periodic table that comes with the game a. Using the Atom Building Game, build a helium atom using two protons (green marbles), two neutrons (blue marbles), and two electrons (yellow marbles). Place the green and blue marbles close together in the nucleus of the board. Place the electrons in the first energy level (the nearest one to the nucleus). What is the total charge of the subatomic particles in the nucleus of this atom? b. According to the rules for electromagnetic force, what should happen to these two protons in the nucleus when they are close together? Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 1

12 B What keeps the nucleus from flying apart? Another atomic force that holds an atom together is called strong nuclear force. Strong nuclear force holds the positively charged nucleus together. This force only works when the subatomic particles are very close together. If the particles are too far apart, electromagnetic force takes over and causes the particles to repel each other. Here are the rules for strong nuclear force: Strong nuclear force holds protons and protons together when they are very close. Strong nuclear force holds neutrons and neutrons together when they are very close. Strong nuclear force holds protons and neutrons together when they are very close. a. In the diagram below, why do you think there are more arrows representing strong nuclear force than there are representing electromagnetic force? b. In your own words, describe how electromagnetic and strong nuclear forces hold an atom together. C Introduction to the Atomic Challenge Game Atomic Challenge is a game that you will play using the Atom Building Game. To play this game you need to understand the information on the periodic table. Take some time now to go over the periodic table in your group. Work together until everyone understands the difference between the atomic number and the mass number for an atom, and the difference between an ion and an isotope. Two more terms that you will need to understand are stable and neutral. The mass numbers of all stable isotopes of the elements are listed on the periodic table. Neutral atoms have equal numbers of protons and electrons. 2 Copyright 2009 CPO Science Can be duplicated for classroom use

13 Investigation A2 For each of these terms, write a sentence that shows you understand its definition. a. atomic number b. mass number c. ion d. isotope e. stable f. neutral Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 3

14 D E Setting up 1. Each Atom Building Game board can have four players. Each player should use one of the four pockets at the corners. 2. Each player should start with the following marbles in their pocket: 6 blue marbles (neutrons) 5 green marbles (protons) 5 yellow marbles (electrons) 3. The remaining marbles stay in the containers and are the bank. Players may need to trade marbles with the bank later in the game. The game of Atomic Challenge The object of the game is to play all your marbles by adding them to the board to make neutral, stable atoms. The first player to run out of marbles wins. After each turn, you must identify the atom you made. For example, after a play you might say lithium six if the marbles you added made an atom with 3 protons (green marbles), 3 neutrons (blue marbles), and 3 electrons (yellow marbles). Each player takes turns adding up to 5 marbles to the atom. Marbles must be added according to these rules for building atoms: 1. The number of protons matches the atomic number of the atom. Number of green marbles = Atomic number 2. The total number of protons and neutrons equals one of the mass numbers for that element. Green marbles + Blue marbles = Mass number 3. The number of electrons and protons match. Number of yellow marbles = Number of green marbles 4. Protons and neutrons go in the nucleus. Only green and blue marbles in the center of the board. 5. Electrons go in the energy levels. Only yellow marbles in the energy levels. Example move: In the graphic above, lithium-7, with 3 protons, 4 neutrons, and 3 electrons, is represented on the Atom Building Game board. If 1 proton (green marble), 1 blue marble (neutron), and 1 electron (yellow marble) are added, the atom becomes beryllium-9. Beryllium has 4 protons, 5 neutrons, and 4 electrons. 4 Copyright 2009 CPO Science Can be duplicated for classroom use

15 F Additional rules Investigation A2 1. You can add no more than 5 marbles per turn. The 5 marbles can include any mix of colors, such as 2 green, 1 blue, and 2 yellow. You may not always be able to add 5 marbles; sometimes you will only be able to add 3 or 4 and still make a real atom. 2. You can challenge a move. After each player s turn, look at the periodic table that comes with the Atom Building Game to see whether the atom is correct or not. If the atom has been incorrectly built or identified, you can challenge the move. A player that makes an atom incorrectly during his or her turn must take the marbles back and does not get to try again until the next turn. The next player then takes a turn. 3. A player can trade marbles with the bank INSTEAD of taking his or her turn. You can take as many marbles, and of as many colors, as you need, but you must take at least as many total marbles as you put in. For example you can trade 2 yellows for 1 yellow, 1 blue, and 1 green. You can put in 2 and take 3, but you cannot put in 2 and take only 1 back. After you have completed a game of Atomic Challenge, answer the following questions. G What did you learn? a. What atomic force keeps electrons in place around the nucleus of an atom? b. What atomic force holds the nucleus of an atom together? Why is this force necessary? c. What is the atomic number of sodium? d. How many protons does sodium have? e. How many isotopes does calcium have? Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 5

16 f. What is the mass number of beryllium? g. What is the charge on a bromine atom that has 35 protons and 36 electrons? h. What do you call an atom that has a positive or a negative charge? i. What does it mean when an atom is stable and neutral? j. The Atom Building Game is a model of an atom. In your own words, define the term model. Include in your answer why models are useful. k. Describe three ways in which the Atom Building Game is like a real atom and three ways it is not. 6 Copyright 2009 CPO Science Can be duplicated for classroom use

17 Investigation A2 Assessment 1. An Atom Building Game has 16 green marbles, 16 blue marbles, and 18 yellow marbles. Answer the following questions based on this information. a. What atom is represented on the Atom Building Game board? b. What is the total charge of this atom? c. What would you need to do to make this atom neutral? 2. Atoms of an element can have more than one mass number, but only one atomic number. Why? 3. What is the difference between a stable atom and a neutral atom? Can an atom be both stable and neutral? 4. Why is the periodic table of the elements an important tool in science? Come up with as many reasons as you can to explain why the periodic table is so useful. Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 7

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19 A3 Building Molecules What is a molecule? When atoms combine with other atoms, they form molecules. The number of electrons in the outermost energy level is important to understanding why atoms, like hydrogen and oxygen, combine to form molecules. Hydrogen and oxygen atoms combine to form water molecules. A What is a compound? Investigation A3 Materials you use can be either elements or compounds. Elements are made of only one kind of atom. Gold is an example of an element. A piece of pure gold contains billions of gold atoms and no other types of atoms. Compounds are made of two or more kinds of atoms. Table salt an example of a compound. The smallest particle of salt that exists is called a molecule. Each grain of salt in your salt shaker contains billions of salt molecules. Each salt molecule contains one sodium (Na) atom and one chlorine (Cl) atom. Another name for table salt is sodium chloride, which can be abbreviated NaCl. Use the above information to complete the table below. Materials One Atom Building Game with marbles. Periodic table that comes with the game Common name of material What atoms are in the material? Is the material an element or a compound? salt sodium (Na) and chlorine (Cl) compound diamond carbon (C) silver silver (Ag) sugar carbon (C), hydrogen (H), oxygen (O) iron iron (Fe) rust iron (Fe) and oxygen (O) Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 1

20 B Outermost energy levels The reason atoms combine with other atoms to make compounds has to do with the electrons in the outermost energy level. The outermost energy level is the one farthest from the nucleus of the atom. Use the Atom Building Game to build a neon- 20 atom. When you add electrons (yellow marbles) to an atom, fill the energy level closest to the nucleus first before filling the next energy level. a. How many electrons are in the outermost energy level of your neon-20 atom? b. Are there any empty spaces in the outermost energy level of the neon-20 atom? c. Do you think a neon atom would combine with another atom to form a compound? Why or why not? C Combining atoms For this part of the investigation, your group will pair up with another group in your class. When you have paired up, decide which group will build a sodium-23 atom and which will build a chlorine-35 atom. After you have built these atoms, place them close together and answer the questions below. 2 Copyright 2009 CPO Science Can be duplicated for classroom use

21 Investigation A3 a. How many electrons does sodium have in its outermost level? How many empty spaces does it have in its outermost level? b. How many electrons does chlorine have in its outermost level? How many empty spaces does it have in its outermost level? c. Sodium and chlorine combine to form a compound known as sodium chloride. You know this compound as table salt. Why do you think these two atoms tend to combine with each other? D What is a chemical bond? When two atoms combine their electrons to fill the outermost energy level, we say that they have formed a chemical bond. A group of atoms connected by bonds is called a molecule. In part 3, you made a molecule with only two atoms. Molecules can also be made of more than two atoms. For the next exercise, you will need to work with other groups in your class to make a water molecule using Atom Building Game boards. Water molecules contain one oxygen atom and some hydrogen atoms. a. Make oxygen-16 with your Atom Building Game board. How many hydrogen atoms will you need to complete the outermost energy level of the oxygen? b. Once you have figured out how many hydrogen atoms you need, get together with the same number of groups in your class. With the other groups, place the boards together to make the water molecule. Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 3

22 c. Do you think water is an element or a compound? Explain your answer. d. Complete the chemical formula for water (see diagram to the right). Write the number of hydrogen atoms in a water molecule in the blank next to the symbol for hydrogen (H). e. What does a chemical formula tell you about a compound? f. In the case of the neon-20 atom, the molecule of sodium chloride, and the molecule of water, how many electrons, in total, were in the outermost energy levels? Why do you think atoms combine with other atoms? 4 Copyright 2009 CPO Science Can be duplicated for classroom use

23 Investigation A3 Assessment 1. Explain the difference between an element and a compound. Give one example of each. 2. Sodium and chlorine combine to form a molecule of table salt. a. Why are sodium and chlorine a good match for making a molecule? b. Fluorine has the same number of electrons in its outermost energy level as sodium. How many sodium atoms do you think will combine with fluorine? Explain your reasoning. 3. Which one of the three different subatomic particles in an atom is involved in forming bonds between atoms? Why do you think the other two kinds of subatomic particles are not involved in forming bonds? 4. Look at the periodic table. The last column (group 18) contains a group of elements called the noble gases. The atoms of these elements do not combine with other atoms to form compounds. a. How many electrons do you think atoms of the noble gases have in their outermost energy levels? b. Explain why noble gases do not combine with other atoms to make compounds. Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 5

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25 B1 Nuclear Reactions Game How are elements organized on the periodic table? In this investigation, you will play a game called Nuclear Reactions using the Atom Building Game and the periodic table that comes with the game. By playing this game, you will learn about the organization of the periodic table. A Introduction to Nuclear Reactions Investigation B1 The elements on the periodic table are arranged by atomic number, from lowest to highest. The atomic number equals the number of protons in the nucleus of an atom. The atomic number also indicates the number of electrons in an atom. Each element has a unique atomic number. Isotopes are atoms with the same number of protons, but different numbers of neutrons. Isotopes of an element have a different mass numbers. The mass number of an isotope indicates how many protons and neutrons are in the nucleus of the isotope. The periodic table shows the mass numbers of the stable isotopes of each element. Materials One Atom Building Game with marbles. Periodic table that comes with the game Nuclear reaction cards Playing Nuclear Reactions involves simulating nuclear reactions. To win the game, you will need to quickly figure out which nuclear reactions will make real atoms. The game is similar to the processes by which the elements of the periodic table were created inside stars. At the center of a star, nuclear reactions combine atoms to make new elements. We believe all the elements of the periodic table that are heavier than lithium were created inside stars through nuclear reactions. The process gives off a huge amount of energy that we experience as light. The energy from nuclear reactions in the sun is what makes life on Earth possible. If you were to add one, two, or four more neutrons to lithium-7 you would have created lithium-8, lithium-9, and lithium-11, respectively. Each of these isotopes of lithium is radioactive, which means that the atomic force in the nucleus (called strong nuclear force) is not strong enough to hold these atoms together. The nuclei of these atoms fly apart. The goal of Nuclear Reactions is to earn points by creating atoms that are stable (not radioactive) and neutrally charged (not ions). Remember that ions are atoms that have different numbers of protons and electrons and so have a charge. Each player starts with 8 protons, 8 electrons, and 8 neutrons in his or her pocket of the Atomic Building Game board. The game will last for about half an hour. The first player to gain 20 points wins. Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 1

26 B Playing Nuclear Reactions To begin, each player is dealt five cards from the deck of Nuclear Reactions cards. These are held and not shown to anyone else. Players take turns, choosing which card to play each turn, and adding or subtracting particles from the atom as instructed on the card. For example, playing an "Add 2 Electrons" card would mean you place two yellow marbles in the atom. Subatomic particles that are added or subtracted from the atom must come from or be placed in your own pocket. You may not play a card for which you do not have the right marbles. For example, a player with only 2 protons left cannot play an Add 3 Protons card. Each time you play a card, draw a new card from the deck so that you always have five. Played cards can be shuffled and reused as needed. C Scoring points Points are scored depending on the atom you create. You will need to use the periodic table to determine your strategy and points earned. In particular, it is useful to know which cards to play to get to stable atoms, neutral atoms, or stable and neutral atoms. The diagram below illustrates the three rules for playing the game. Rule #1: The number of protons (green marbles) matches the atomic number. Rule #2: The number of protons (green marbles) plus the number of neutrons (blue marbles) equals one of the correct mass numbers for the element of Rule #1. This move creates a stable atom. Rule #3: The number of electrons (yellow marbles) equals the number of protons (green marbles). This move creates a neutral atom. 2 Copyright 2009 CPO Science Can be duplicated for classroom use

27 Investigation B1 You score 1 point if your move creates or leaves a stable atom. For example, you score 1 point by adding a neutron to a nucleus with 6 protons and 5 neutrons. The resulting atom is carbon-12 which is stable. The next player can also score a point by adding another neutron, making carbon-13. To get the nucleus right you need to satisfy rules #1 and #2. You score 1 point for adding or taking electrons or protons from the atom if your move creates or leaves a neutral atom. A neutral atom has the same number of electrons and protons. Getting the electrons and protons to balance satisfies rule #3. You score 3 points (the best move) when you add or take particles from the atom and your move creates a stable and neutral atom. For example, taking a neutron from a stable, neutral carbon-13 atom leaves a stable, neutral carbon-12 atom, scoring 3 points. In other words, you get 3 points if your turn makes an atom that meets all three rules. D Additional rules Taking a turn When it is your turn, you must either play a card and add or subtract marbles from the atom, or trade in your cards for a new set of five. Trading in cards You may trade in all your cards at any time by forfeiting a turn. You have to trade all your cards in at once. Shuffle the deck before taking new cards. Using the periodic table All players should use a periodic table to play the game. The marble bank You may choose to use either of two versions of the marble bank. In version 1, players take marbles from the bank at any time so that they have enough to play the game. In version 2, players must lose a turn to draw marbles from the bank, and may draw no more than 5 total marbles (of any colors) in one turn. Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 3

28 E Nuclear reactions There are two kinds of nuclear reactions, fusion and fission. These kinds of reactions only involve the nuclei of atoms. The word nuclei is the plural form of the word nucleus. Fusion involves the combination of two elements with small mass numbers to make an element with a larger mass number. In the top diagram to the right, nuclei are fused, a particle is emitted, and a lot of energy is released. The reaction in the diagram involves the fusion of hydrogen-3 (1 proton + 2 neutrons) with hydrogen-2 (1 proton + 1 neutron) to make a helium-4, a neutron, and energy. In the diagram, the black dots are protons; the gray dots are neutrons. Fission involves the splitting of an element with a large mass number into elements with smaller mass numbers. The diagram to the right shows a nuclear fission chain reaction. Nuclear fission can be started when a neutron (gray ball) bombards a nucleus (black ball). A chain reaction results. A free neutron (step A) bombards a nucleus (step B) and the nucleus splits into nuclei with smaller mass numbers. More neutrons are also released (step C). These neutrons then bombard other nuclei. Nuclear reactors control fission (and energy production) by capturing neutrons to start, slow, or stop the chain reaction. The questions below will help you better understand fission and fusion. Use the Atom Building Game to work through the questions. a. Demonstrate the fusion reaction diagram using the Atom Building Game board. Collect enough marbles (protons, neutrons, and electrons) to build a hydrogen-3 atom (this is a radioactive isotope). Then collect enough marbles to build a hydrogen-2 atom. Place all these marbles in the correct places on the Atom Building Game board. Remove one neutron and hold it in your hand. What element is represented on the board? Why was it important to take away one neutron? b. Collect enough marbles (protons, neutrons, and electrons) to build lithium-6. Then collect enough marbles to build boron-11. Place all these marbles in the correct places on the Atom Building Game board. What element is represented on the board? Was this activity an example of fusion or fission? 4 Copyright 2009 CPO Science Can be duplicated for classroom use

29 Investigation B1 c. Is the atom that results from the combination of lithium-6 and boron-11 a stable or a radioactive isotope? Is the atom an ion or neutral? d. Now build boron-10 on the Atom Building Game board. How many protons, neutrons, and electrons did you need to add to the board to make fluorine-19? If you were to add these subatomic particles to boron-10, would this represent fusion or fission? e. Suppose you split a uranium-238 atom. If you have to break it into two pieces, name two elements that could be formed. Be sure that your two elements use up all the neutrons and protons in the uranium. Is either of your two elements a stable isotope or is one (or are both) radioactive? Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 5

30 Assessment 1. Identify the mystery atoms that go with the clues. Some clues may have more than one right answer. a. An atomic number of 29. b. A mass number of 54. c. The element has four isotopes. d. Atoms of the element each have 65 protons. e. Atoms of the element have three neutrons. 2. Describe the organization of the periodic table. How does this organization help you find information about elements? 3. Describe the term radioactive. Explain why atoms of certain elements undergo radioactive decay. 4. There are two Atom Building Game boards on a table. The first board is set up to represent an atom that has 19 protons, 22 neutrons, and 18 electrons. The second board is set up to represent an atom that has 43 protons, 55 neutrons, and 43 electrons. Which of these atoms is an ion and which is a radioactive isotope? In your answer, justify your answer and explain the difference between the terms ion and isotope. 6 Copyright 2009 CPO Science Can be duplicated for classroom use

31 B2 Bonding and Molecules Why do atoms form chemical bonds? Most of the matter on Earth is in the form of compounds. Even when a substance exists as a pure element, it tends eventually to combine with other elements. For example, if you leave an iron nail outside in the rain, it will quickly combine with the oxygen in the air to form iron oxide, better known as rust. In this investigation you will build models of atoms and discover one of the fundamental ideas in chemistry: how electrons are involved in the formation of chemical bonds. A Reviewing atomic structure Let s review what you already know about atoms: A neutral atom has the same number of electrons and protons. The electrons occupy energy levels surrounding the nucleus. Electrons are attracted to the nucleus, so they fill the lower energy levels first. Once a given level is full, electrons start filling the next level. B How many electrons are in the outermost level? Investigation B2 Materials One Atom Building Game with marbles. Periodic table that comes with the game Using the Atom Building Game, build each element in the table. For each element, record the atomic number, the number of electrons, and the number of empty spaces in the outermost energy level. Element Atomic number Number of electrons in outermost level hydrogen helium lithium fluorine neon sodium chlorine argon potassium Number of empty spaces in outermost level Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 1

32 C What are valence electrons? The electrons in the outermost level of an atom are called valence electrons. These are the electrons involved in forming chemical bonds. Examine the table you just completed and record the answers to the following questions: a. What do lithium, sodium, and potassium have in common? b. What do fluorine and chlorine have in common? c. What do neon and argon have in common? d. What is the relationship between the number of valence electrons and the placement of elements on the periodic table? D Modeling a chemical bond Atoms that have a complete outermost level are stable. If there are empty spaces, an atom will either gain, lose, or share electrons with another atom in order to complete its outermost level and become stable. When atoms gain, lose, or share electrons with another atom, they form chemical bonds. Using two Atom Building Games, build a sodium atom and a chlorine atom. Put them next to each other and answer the questions below. a. In order to complete its outermost level, do you think sodium will tend to lose its only valence electron, or gain seven electrons? Explain your answer. 2 Copyright 2009 CPO Science Can be duplicated for classroom use

33 Investigation B2 b. In order to complete its outermost level, do you think chlorine will tend to lose all of its valence electrons or gain one electron? Explain your answer. c. Why do you think these two atoms bond together to form a molecule? In your answer, describe what you think happens to the electrons when sodium and chlorine form a chemical bond. E Determining oxidation numbers An element s oxidation number is equal to the charge an atom has when it ionizes, that is, gains or loses electrons. Use your models of sodium and chlorine to answer the questions below. a. Remove the valence electron from sodium. What has happened to the balance of positive and negative charges? What is sodium s oxidation number? b. Move the electron you took from sodium into the chlorine. What happens to chlorine s charge when it gains the electron from the sodium atom? What is chlorine s oxidation number? c. When sodium and chlorine form a chemical bond, what is the overall charge of the molecule? Why do you think sodium and chlorine combine in a 1:1 ratio? Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 3

34 Assessment 1. To the right is a diagram of the periodic table with some columns labeled with letters. In the table below, write the number of electrons that are in the outermost energy level of the atoms from the shaded areas of the columns. Column letter Number of electrons in the outermost energy level A B C D E F G H 2. Fill in the atomic number and number of valence electrons for each element in the table. Using your rules for making molecules, write one element with which the element in the first column may bond. The first row has been completed for you as an example. Element Atomic number Number of valence electrons in element Bonding partner 3. Which atoms on the periodic table are the least likely to ionize? Why? Number of valence electrons in bonding partner hydrogen 1 1 fluorine 7 helium sulfur silicon oxygen carbon 4 Copyright 2009 CPO Science Can be duplicated for classroom use

35 C1 Electrons and the Periodic Table How is the periodic table organized? An electron configuration is a symbolic way to describe how electrons are arranged around the nucleus of an atom. In this investigation, you will use the Atom Building Game to discover the relationship between how electrons are arranged in atoms and the placement of elements on the periodic table. A Where do you find electrons in an atom? Investigation C1 A common way to understand the structure of an atom is to think of the nucleus of an atom as the size of a marble. In this case, the outer boundary of the atom would be the size of a football stadium. If we had an atom that was the size of a football stadium, we could easily locate the protons and neutrons. We would simply have to find the marble in the center of the stadium. However, how could we say exactly where the electrons would be? Electrons are continuously moving around the nucleus of an atom. However, the place where a single electron can be found most often is identified by its energy level and electron orbital. The Atom Building Game is a model of an atom that includes five of the possible seven energy levels and three kinds of electron orbitals. The energy levels surround the center of the board (the nucleus). The orbitals are represented by the pockets for the marbles at each energy level. You will notice that the pockets for the marbles in these energy levels are either single or in groups of three or five. These arrangements represent electron orbitals. s orbitals: The single pockets represent s orbitals. Two electrons are associated with an s orbital for a given energy level. This is why two single pockets are always across from each other on the game board. Find s orbitals in each energy level on the board. p orbitals: The pockets that are in groups of three represent p orbitals. Six electrons fill the p orbitals for a given energy level. This is why there are two sets of three pockets to represent the p orbitals for an energy level. The pockets represent three p orbitals holding two electrons each. Find the p orbitals on the second, third, fourth, and fifth energy levels on the board. d orbitals: The pockets that are in groups of five represent d orbitals. Ten electrons fill d orbitals for a given energy level. This is why there are two sets of five pockets to represent the d orbitals for a given energy level. The pockets represent five d orbitals holding two electrons each. Find the d orbitals on the fourth and fifth energy levels on the board. Materials One Atom Building Game with marbles. Periodic table that comes with the game Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 1

36 . Compare the information in Table 1 with the arrangement of pockets for marbles in the energy levels of the Atom Building Game. Then, fill in the last column of Table 1. Table 1: Electrons in each energy level Energy level Type of electron orbital Number of electron orbitals Number of electrons in the orbitals (# of electron orbitals x 2) Total number of electrons in each energy level 1 s s 1 2 p s 1 2 p s 1 2 p 3 6 d s 1 2 p 3 6 d 5 10 B More on electron orbitals There is one orbital that we have not mentioned: the f orbital. The f orbitals are in the 6th and 7th energy levels. The 6th and 7th energy levels both have seven f orbitals. Fourteen electrons fill the seven f orbitals (two electrons per orbital). Atoms that have f orbitals are shown at the bottom of the periodic table. Red arrows highlight the two rows. Atoms with f orbitals come after lanthanum and actinium. Although lanthanum and actinium are at the start of the row, they belong next to barium and radium and they do not have f orbitals. The f orbitals are not included on the Atom Building Game board. For this reason, the range of atoms that you can build (using only protons and electrons) with the Atom Building Game board goes from hydrogen to xenon. Elements larger than xenon have electrons in the 6th and 7th energy levels. 2 Copyright 2009 CPO Science Can be duplicated for classroom use

37 Investigation C1 a. How many pockets for electrons are on the Atom Building Game board? b. Can you build xenon-136 using the Atom Building Game? Explain why or why not. c. Name one atom that you cannot build using the Atom Building Game board. d. Name an atom that has electrons in an f orbital. Where is this atom on the periodic table? C Electron configurations Electrons fill the energy levels and electron orbitals in a certain order. The position that has the lowest energy is filled first. The position that has the lowest energy is in the first energy level (the level closest to the nucleus), in the s orbital. This electron s position is represented by writing: 1s 1. The order in which electrons fill all seven energy levels (1-7) and all electron orbitals (s, p, d, and f) is listed in Table 2. This order (going from left to right) is called an electron configuration. Lowest energy Table 2: Electron configuration for ununoctium These energy levels are represented These energy levels are not on on the Atom Building Game board the Atom Building Game Board Highest energy s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 6 7s 2 5f 14 6d 10 7p 6 Each element on the periodic table has a unique electron configuration. For example, hydrogen s electron configuration is 1s 1 and carbon s electron configuration is 1s 2 2s 2 2p 2. The electron configuration in Table 2 (which includes all the energy levels and orbitals) is for ununoctium (Uuo). Find ununoctium on the periodic table and the answer the questions on the next page. Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 3

38 a. Based on ununoctium s electron configuration, what is the maximum number of electrons that can occupy each orbital (s,p,d and f)? b. How many electrons does ununoctium have? c. Does ununoctium have any stable isotopes? d. What do you think the name ununoctium means? In the 4th, 5th, 6th, and 7th energy levels, you will notice orbitals with numbers from a lower energy level. For example, the 4s and 4p orbitals, and the 3d orbital are all in the 4th energy level on the Atom Building Game board. This is because the third and fourth energy levels overlap each other. The 4s orbital is filled before the 3d orbital. This is because the 4s orbital has a lower energy than the 3d orbital. While technically, the electrons in the 3d orbital are in the third energy level, they have as much energy as electrons in the fourth energy level. For this reason, they are shown in the fourth energy level on the Atom Building Game board. D How do you fill the electron orbitals on the Atom Building Game board? When building atoms with the Atom Building Game, it is important to add electrons in the correct order. Follow these simple rules as you add electrons: Fill one energy level before moving to the next energy level. Five energy levels are represented on the Atom Building Game board. For the first through the third energy level: First fill the s orbital pockets, and then the p orbital pockets. For the fourth and fifth energy levels: First fill the s orbital pockets, then the d pockets, and finally the p pockets. 4 Copyright 2009 CPO Science Can be duplicated for classroom use

39 Investigation C1 Build all of the atoms on the periodic table, from hydrogen up to krypton, using the Atom Building Game. For this activity, you do not need to worry about the protons and neutrons. As you add electrons, write the electron configuration for each atom in Table 3. Table 3: Atomic numbers, symbols, and electron configurations of the first 36 elements 1. H 2. He 3. Li 4. Be 5. B 6. C 7. N 8. O 9. F 10. Ne 11. Na 12. Mg 13. Al 14. Si 15. P 16. S 17. Cl 18. Ar 19. K 20. Ca 21. Sc 22. Ti 23. V 24. Cr 25. Mn 26. Fe 27. Co 28. Ni 29. Cu 30. Zn 31. Ga 32. Ge 33. As 34. Se 35. Br 36. Kr E Electron configurations and the periodic table Use the electron configurations in Table 3, and the diagram below, to answer questions a through f. Note: The outermost energy level refers to the level with the highest number. Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 5

40 a. How are the numbers of the energy levels (1-7) related to the organization of the periodic table? b. Which elements have a completely filled outermost energy level? Where are these elements on the periodic table? c. Which elements have only one electron in the outermost energy level? Where are these elements on the periodic table? d. Which elements have only two electrons in the outermost energy level? Where are these elements on the periodic table? e. Which elements (besides hydrogen) need only one electron to have completely filled outermost s and p orbitals? Where are these elements on the periodic table? f. What is the relationship between group number, location, and number of outermost electrons of the main group elements? g. What is the relationship between group number and the electron configurations of the transition metals? 6 Copyright 2009 CPO Science Can be duplicated for classroom use

41 Assessment Investigation C1 1. What information can you get from the periodic table? Define any terms that you use. 2. What two pieces of information do you need to know about an electron in order to figure out where it probably is located around the nucleus of an atom? 3. Explain the differences among s, p, d, and f electron orbitals. 4. The electron configurations of some elements are listed below. Use the periodic table to identify the element that is represented by each electron configuration. Electron configuration 1s 2 2s 1 1s 2 2s 2 2p 6 3s 2 3p 3 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 1s 2 2s 2 2p 5 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 7 Number of electrons represented Element Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 7

42 Extra space for notes: 8 Copyright 2009 CPO Science Can be duplicated for classroom use

43 C2 Energy and the Quantum Theory How do atoms make light? The electrons in an atom are organized into energy levels. You can think of energy levels like a staircase where the electrons can be on one step or another but cannot exist in-between steps. When an electron changes levels, the atom absorbs or emits energy, often in the form of light. This investigation will teach you a challenging and fun game that simulates how atoms exchange energy through light. The process is fundamentally how a laser works. Investigation C2 Materials One Atom Building Game with marbles. Periodic table that comes with the game Photons and lasers cards A The neon atom 1. Build a neon atom with 10 each of protons (green marbles), neutrons (blue marbles) and electrons (yellow marbles). 2. Set the electrons in the lowest spaces possible. 3. Find the following cards in the Photons and Lasers can Pump 1 (red) Pump 2 (yellow) Laser 1 (red) B How atoms exchange energy a. Explain the meaning of the term ground state when applied to an atom. b. Can the second energy level of neon hold any more electrons? How does this affect neon s chemical properties and position on the periodic table? Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 1

44 c. Take the red pump 1 card from your hand and put it on the atom board. Move one electron from level 2 to level 3. Explain what this sequence of actions represents in a real atom. d. Take the yellow pump 2 card from your hand and put it on the atom board. Move any one electron up 2 levels. Explain what this sequence of actions represents in a real atom. e. Take the red laser 1 card from your hand and put it on the atom board. Move any one electron down one level. Explain what this sequence of actions represents in a real atom. C The photons and lasers game 1. Each player starts with 5 cards and plays one per turn. Draw a new card to maintain a hand of Playing a pump card allows the player to advance one electron up by the number of levels shown on the card (1 4). No points are scored by playing pump cards. 3. Playing a laser card allows the player to drop electrons from one level to a lower level. The player scores one point per electron per level. For example, moving 2 electrons down 2 levels scores 4 points. 2 Copyright 2009 CPO Science Can be duplicated for classroom use

45 Investigation C2 D 4. Rules for playing laser cards: Electrons can only be moved down if there are empty states for then to move to. Electrons can only be moved from one level in a turn. If the card says laser 2 then each electron must move 2 levels. 5. Play the game until someone in your group wins by reaching ten points. Thinking about what you learned a. What does the term excited state mean with respect to energy and atoms? b. What physical principle prevents two electrons from moving into the same state? c. In order of increasing energy, arrange the following colors of light: blue, red, green, yellow. d. Could an atom emit one photon of blue light after absorbing only one photon of red light? Explain why or why not. e. Suppose a real atom had energy levels just like the game. Could this atom make bluegreen light with an energy in between blue and green? Explain what colors this atom could make. Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 3

46 Assessment 1. Next to each energy level, write the total number of electrons that can fit in each level. a. 1st energy level b. 2nd energy level c. 3rd energy level d. 4th energy level e. 5th energy level 2. Many types of electric lights contain gaseous elements. For example, fluorescent lighting bulbs contain mercury. Explain how these gases in the bulbs might contribute to the production of light. Think about the conditions needed for an element to produce light. 3. A common demonstration in a chemistry laboratory involves placing a special wire holding a small amount of a salt solution (such as sodium chloride) in the flame of a Bunsen burner. The result is that certain colors are produced as the flame burns the solution off the wire. Some solutions produce yellow light, some produce red light, and some produce other colors like green and violet. Explain what is going on in this situation. What causes these different colors to be produced? What is the role of the Bunsen burner? 4. The word laser is an acronym that stands for the phrase Light Amplification by Stimulated Emission of Radiation. Think about each part of this phrase. Explain why each part is important to describing how a laser works. 4 Copyright 2009 CPO Science Can be duplicated for classroom use

47 C3 Valence Electrons and Molecules What is the role of electrons in forming molecules? Some objects, such as gold and silver jewelry, are made of pure elements. But the majority of things we use, eat, and wear are made of compounds. Compounds are substances that are made of two or more different kinds of atoms. The smallest unit of a compound that retains the properties of the compound is a molecule. In this investigation you will use the Atom Building Game to learn how and why atoms form chemical bonds. A How many electrons are in the outermost level? Investigation C3 Materials One Atom Building Game with marbles. Periodic table that comes with the game Use the Atom Building Game to build each element in Table 1. For each element, record the atomic number, the number of electrons and the number of empty spaces in the outermost energy level. Then answer the questions. Table 1: Electrons and energy levels Element Atomic number Number of electrons in the outermost energy level Number of empty spaces in the outermost level lithium potassium fluorine bromine neon krypton a. What do lithium and potassium have in common? b. What do fluorine and chlorine have in common? Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 1

48 c. What do neon and argon have in common? B What are valence electrons? The electrons in the s and p orbitals of the outermost energy level are called valence electrons. These electrons are involved in forming the chemical bonds that hold the atoms in a compound together. a. How many electrons are in an s orbital of a given energy level? b. How many electrons are in the three p orbitals of a given energy level? c. How many electrons are in a s orbital plus the three p orbitals for a given energy level? d. If valence electrons include the electrons in the s and p orbitals for an energy level, what is the maximum number of valence electrons that an atom can have? e. Use Table 2 below to group the atoms from Table 1 according to their number of valence electrons. In the first column, write a number of valence electrons. In the second column, write the names of the elements that have that number of valence electrons. Number of valence electrons Table 2: Elements and valence electrons Elements 2 Copyright 2009 CPO Science Can be duplicated for classroom use

49 Investigation C3 f. How is the placement of an element on the periodic table related the number of valence electrons the element has? C Modeling a chemical bond If there are empty spaces in the outermost energy level of an atom, it will react with another atom in order to gain, lose, or share electrons to fill in these spaces. When atoms gain, lose, or share electrons with another atom, they form a chemical bond. Join with another group in your class. Using two Atom Building Game boards, build a sodium atom and a chlorine atom. Place the two boards next to each other and answer the questions below. a. In order to fill its outermost energy level, do you think sodium will lose its only valence electron, or gain seven electrons? Explain your answer. b. When sodium loses one electron, what does the new outermost energy level look like? c. In order to fill its outermost energy level, do you think chlorine will tend to lose all seven of its valence electrons or gain one electron? Explain your answer. Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 3

50 d. Describe the outermost energy level of chlorine with one more electron added. e. Why do you think these two atoms bond together to form a molecule? In your answer, describe what you think happens to the electrons when sodium and chlorine form a chemical bond. D Determining oxidation numbers An element s oxidation number is equal to the charge an atom has when it ionizes. When an atom ionizes, it gains or loses electrons and becomes an ion. Remember that an ion is an atom that has a charge because the numbers of protons and electrons in the atom are not equal. Knowing an atom s oxidation number is helpful in determining the number of electrons an atom contributes during bond formation. Use your models of sodium and chlorine to answer the questions below. a. Remove the valence electron from sodium. What is the total charge on the atom now? b. The total charge on sodium after it ionizes is equal to sodium s oxidation number. What is sodium s oxidation number? c. Move the electron you took from sodium into the chlorine. What happens to chlorine s total charge when it gains the electron from the sodium atom? d. In its ionized state, chlorine has a full outermost energy level. What is chlorine s oxidation number? e. When sodium and chlorine form a chemical bond, what is the overall charge of the molecule? f. Sodium and chlorine combine in a 1:1 ratio. This means for every one sodium atom, there is a chlorine atom. Why do you think these atoms combine in this way? 4 Copyright 2009 CPO Science Can be duplicated for classroom use

51 E Making molecules Investigation C3 A molecule of a sodium atom and a chlorine atom can be represented using the symbols for sodium (Na) and chlorine (Cl). NaCl is the chemical formula for a molecule that includes one sodium atom and one chlorine atom. This molecule is also known as table salt. The molecules in Table 3 are represented by their molecular formulas. The small numbers, or subscripts, next to the symbol for an atom (like the 2 next to the H in H 2 O) indicate how many atoms there are of this atom in the molecule. The ratio of atoms in each molecule is listed in the second column of the table. Use the two Atom Building Game boards to build each of the two kinds of atoms in these molecules. As you build the atoms, think about these questions: Why do you think some atoms combine in different ratios like 1:1, 2:1 or 1:4? What is the role of valence electrons in forming molecules? Does the placement of an atom on the periodic table tell you anything about what atoms it combines with to form a molecule? Use your answers to these questions to help you figure out three rules for predicting molecules. F Average atomic mass Table 3: Chemical formulas and ratios Chemical formula Ratio of first atom to second atom (first atom:second atom) NaCl 1:1 CaO 1:1 H 2 O 2:1 CH 4 1:4 By using the formula below, you can calculate the number of neutrons in an atom. Number of protons + Number of neutrons = Mass number The mass number of an element is equal to the number of subatomic particles in the nucleus (protons plus neutrons). The mass number can also be used as the mass (in grams) of a certain number of atoms of the element. The certain number of these atoms is called Avogadro s number and it is equal to atoms. This amount of atoms is also referred to as a mole of atoms. If you had atoms of any element, you would have a mole of that element. The two stable isotopes of silver are silver-107 and silver-109. One mole of silver-107 has a mass of 107 grams. One mole of silver-109 has a mass of 109 grams. A mole of an element is a useful measurement because atoms are so small. It is much easier to work with large numbers of atoms rather than single atoms. Another measurement used for working with atoms is average atomic mass. This value is based on the abundance of each isotope. Filling in Table 4 will help you understand average atomic mass. The numbers listed are some possible average atomic masses for silver. In the space next to these values in Table 4, write down what you think these values mean regarding how much of each isotope of silver might be in a sample of silver from nature. Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 5

52 For example, there are two isotopes of silver: silver-107 and silver-109. If the average atomic mass of silver was 107, would there be more silver-107 than silver-109? Would there be any silver-109 on Earth? The answer to the first question is yes, there would be more silver-107, and the answer to the second question is no, there would be no silver-109. An average atomic mass of 107 implies that there are no silver isotopes with a mass of 109. However, an average atomic mass of does imply that there is a small amount of silver isotopes that have a mass number larger than 107. Table 4 Average atomic mass of silver What this number means about the abundance of each isotope of silver in the universe a. The actual average atomic mass of silver is grams per mole. What does this value tell you about the abundance of silver-107 versus silver-109? b. If you have a sample of silver from nature and you were able to select one atom from this sample, what are the chances that you would select a silver-107 atom? c. Bromine has two isotopes: bromine-79 and bromine-81. The abundance of bromine-79 is 50.69%. The abundance of bromine-81 is 49.31%. Based on this information, what is the average atomic mass of bromine? 6 Copyright 2009 CPO Science Can be duplicated for classroom use

53 Assessment Investigation C3 1. Fill in the number of valence electrons for the listed elements in the table below. Element Valence electrons sodium calcium tin nitrogen radon arsenic carbon helium 2. One of the rules that is used for figuring out which atoms will combine to form molecules is called the octet rule. You may have figured out this rule on your own during the investigation. Write a definition of what you think the octet rule is. Use the term valence electrons in your answer. 3. Which atoms on the periodic table are the least likely to ionize? Why? 4. Certain groups of elements on the periodic table are numbered (see diagram to the right). Write down three rules for using the periodic table to help you determine which elements bond with each other. Atom Building Game Copyright 2009 CPO Science Can be duplicated for classroom use 7