CHAPTER REVIEW EVIEW ANSWERS 1. alkaline-earth metals 2. halogens 3. metals. electron affinity 5. actinides 6. answers should involve the transmutation of one element to another by a change in the number of protons in its nucleus. 7. alkali metals 8. electron shielding 9. electronegativity and ionization energy 0. Answers should discuss particle accelerators and the colliding of particles at very high speeds to produce elements of higher atomic numbers. 1. noble gases 2. seven 3. Answers may include brass, steel, sterling silver, pig iron, etc.. Moseley arranged the elements according to their atomic numbers, while Mendeleev had arranged them based on their atomic mass. 5. He left gaps for the elements that he predicted would be discovered and which would have certain properties. 6. His success in predicting the properties of elements that had not yet been discovered gave him credibility. 7. The completion of an energy level determines the points at which the elements begin new periods. 8. It has two valence electrons and six occupied energy levels. 9. With only one proton and one electron, hydrogen does not exhibit the same properties shared by the elements making up any of the groups in the periodic table. 150 USING KEY TERMS CHAPTER REVIEW 1. What group of elements do Ca, Be, and Mg belong to? 2. What group of elements easily gains one valence electron? 3. What category do most of the elements of the periodic table fall under?. What is the term for the energy released when an atom gains an electron? 5. What are elements 90 103 called? 6. Give an example of a nuclear reaction. Describe the process by which it takes place. 7. What are elements in the first group of the periodic table called? 8. What atomic property affects periodic trends down a group in the periodic table? 9. What two atomic properties have an increasing trend as you move across a period? 10. Write a paragraph describing in WRITING your own words how synthetic SKILLS elements are created. Discuss what modification has to be made to the equipment in order to synthesize superheavy elements. 11. Which group of elements has very high ionization energies and very low electron affinities? 12. How many valence electrons does a fluorine atom have? 13. Give an example of an alloy. Assignment Guide Section Questions 1 12, 1 18, 0, 2, 52, 57 2 1 3, 5, 7, 13, 19 26, 1, 6, 8, 50, 51, 55 3, 8, 9, 11, 27 33, 3, 7, 9, 5, 58 6 6, 10, 3, 39, 56 UNDERSTANDING KEY IDEAS How Are Elements Organized? 1. How was Moseley s arrangement of the elements in the periodic table different from Mendeleev s? 15. What did the gaps on Mendeleev s periodic table represent? 16. Why was Mendeleev s periodic table accepted by most chemists? 17. What determines the horizontal arrangement of the periodic table? 18. Why is barium, Ba, placed in Group 2 and in Period 6? Tour of the Periodic Table 19. Why is hydrogen in a class by itself? 20. All halogens are highly reactive. What causes these elements to have similar chemical behavior? 21. What property do the noble gases share? How do the electron configurations of the noble gases give them this shared property? 22. How do the electron configurations of the transition metals differ from those of the metals in Groups 1 and 2? 23. Why is carbon, a nonmetal element, added to iron to make nails? 2. If an element breaks when it is struck with a hammer, could it be a metal? Explain. 25. Why are the lanthanides and actinides placed at the bottom of the periodic table? 26. Explain why the main-group elements are also known as representative elements. 50 Chapter The Periodic Table
Trends in the Periodic Table 27. What periodic trends exist for ionization energy? How does this trend relate to different energy levels? 28. Why don t chemists define atomic radius as the radius of the electron cloud that surrounds a nucleus? 29. How does the periodic trend of atomic radius relate to the addition of electrons? 30. What happens to electron affinity as you move across a period beginning with Group 1? Why do these values change as they do? 31. Identify which trend diagram below describes atomic radius. a. b. c. 32. What periodic trends exist for electronegativity? Explain the factors involved. 33. Why are the melting and boiling points of mercury almost the lowest of the elements in its period? Where Did the Elements Come From? 3. How does nuclear fusion generate energy? 35. What happens in the nucleus of an atom when a transmutation takes place? 36. Why are technetium, promethium, and neptunium considered natural elements even though they are not found on Earth? 37. Why must a synchrotron be used to create a superheavy element? 38. What role did supernovae play in creating the natural elements? 39. What two elements make up most of the matter in a star? MIXED REVIEW 0. Without looking at the periodic table, identify the period and group in which each of the following elements is located. a. [Rn]7s 1 b. [Ar]s 2 c. [Ne]3s 2 3p 6 1. Which of the following ions has the electron configuration of a noble gas: Ca + or Cl? (Hint: Write the electron configuration for each ion.) 2. When 578 kj/mol of energy is supplied, Al loses one valence electron. Write the electron configuration of the ion that forms. 3. Name three periodic trends you encounter in your life.. How do the electron configurations of the lanthanide and actinide elements differ from the electron configurations of the other transition metals? 5. Use the periodic table to describe the chemical properties of the following elements: a. iodine, I b. krypton, Kr c. rubidium, Rb 151 REVIEW ANSWERS 20. All halogens have seven valence electrons and are therefore one electron short of having a full valence shell. As a result, they readily react to acquire this one electron. 21. Noble gases do not normally react with other elements because of the stability resulting from their electron configurations. 22. The outer electrons of Groups 1 and 2 are in s orbitals. The outer electrons of the transition metals are in d orbitals and s orbitals. 23. Pure iron is too soft to make nails. Adding carbon produces a harder alloy. 2. Some metals are brittle. Therefore, this element may be a metal if it is shown to be an excellent conductor of electricity. 25. This arrangement keeps the periodic table conveniently narrow. 26. They exhibit all the properties characteristic of the elements. 27. Ionization energy slightly decreases as you move down a group and increases significantly as you move across a period. Increased distance from the nucleus allows removal of an electron using less energy. 28. Because an electron cloud has no definite boundary, an exact radius is impossible to measure. 29. As electrons are added across a period, they are entering the same principal energy level. The increasing nuclear charge pulls these electrons closer, making the atoms progressively smaller across a period. As electrons are added down a group, they are entering another principal energy level, thus increasing the size of the atom. 30. Electron affinity generally increases because the effective nuclear charge increases. Electron shielding does not play a role because electrons are not added to inner energy levels. Chapter The Periodic Table 151
REVIEW ANSWERS 1. c 2. Electronegativity decreases as you move down a group because of the increasing electron shielding and increases as you move across a period because of the increasing effective nuclear charge. 3. Because the d orbitals are completely filled, mercury forms weaker bonds than most of the other elements in Period 6.. The mass of the fused nuclei is less than that of the mass of the nuclei that created it. This mass is converted to energy during fusion. 5. The number of protons either increases or decreases during a nuclear reaction, producing a different element. 6. These elements can be found elsewhere in the universe and are therefore natural. 7. Only a synchrotron can accelerate nuclei to energies high enough to result in fusion involving massive nuclei. 8. Elements heavier than iron were formed in supernovae. 9. hydrogen and helium 0. a. Period 7, Group 1 b. Period, group 2 c. Period 3, group 18 1. Cl 2. [Ne]3s 2 3. Answers will vary but could include, for example, the pattern of seasons, the repeating school year, the progression of weeks, or the pattern of daily meals.. The lanthanide and actinide elements have partially filled f-electron shells. 5. a. A nonmetal in Group 17, it needs one electron to achieve a noble-gas configuration, which means it is likely to react with elements with which it can obtain one electron, such as an alkali metal. It has a high ionization energy, and thus the formation of positive ions is not likely. 152 6. The electron configuration of argon differs from those of chlorine and potassium by one electron each. Compare the reactivity of these three elements, and relate them to their electron configurations. 7. What trends were first used to classify the elements? What trends were discovered after the elements were classified in the periodic table? 8. Among the main-group elements, what is the relationship between group number and the number of valence electrons among group members? CRITICAL THINKING 9. Consider two main-group elements, A and B. Element A has an ionization energy of 19 kj/mol. Element B has an ionization energy of 1000 kj/mol. Which element is more likely to form a cation? 50. Argon differs from both chlorine and potassium by one proton each. Compare the electron configurations of these three elements to explain the reactivity of these elements. 51. While at an amusement park, you inhale helium from a balloon to make your voice higher pitched. A friend says that helium reacts with and tightens the vocal cords to make your voice have the higher pitch. Could he be correct? Why or why not? 52. In his periodic table, Mendeleev placed Be, Mg, Zn, and Cd in one group and Ca, Sr, Ba, and Pb in another group. Examine the electron configurations of these elements, and explain why Mendeleev grouped the elements this way. 53. The atomic number of yttrium, which follows strontium in the periodic table, exceeds the atomic number of strontium by one. Barium is 18 atomic numbers after strontium but it falls directly beneath strontium in the periodic table. Does strontium share more properties with yttrium or barium? Explain your answer. 5. Examine the following diagram. Explain why the structure shown on the right was drawn to have a smaller radius than the structure on the left. ALTERNATIVE ASSESSMENT 55. Select an alloy. You can choose one mentioned in this book or find another one by checking the library or the Internet. Obtain information on how the alloy is made. Obtain information on how the alloy is used for practical purposes. 56. Construct a model of a synchrotron. Check the library and Internet for information about synchrotrons. You may want to contact a synchrotron facility directly to find out what is currently being done in the field of synthetic elements. 57. In many labeled foods, the mineral content is stated in terms of the mass of the element, in a stated quantity of food. Examine the product labels of the foods you eat. Determine which elements are represented in your food and what function each element serves in the body. Make a poster of foods that are good sources of minerals that you need. CONCEPT MAPPING 58. Use the following terms to create a concept map: atomic number, atoms, electrons, elements, periodic table, and protons. 52 Chapter The Periodic Table
FOCUS ON GRAPHING Study the graph below, and answer the questions that follow. For help in interpreting graphs, see Appendix B, Study Skills for Chemistry. 59. What relationship is represented in the graph shown? 60. What do the numbers on the y-axis represent? 61. In every Period, which Group contains the element with the greatest atomic radius? 62. Why is the axis representing group number drawn the way it is in going from Group 2 to Group 13? 63. Which period shows the greatest change in atomic radius? 6. Notice that the points plotted for the elements in Periods 5 and 6 of Group 2 overlap. What does this overlap indicate? TECHNOLOGY AND LEARNING 65. Graphing Calculator Graphing Atomic Radius Vs. Atomic Number The graphing calculator can run a program that graphs data such as atomic radius versus atomic number. Graphing the data within the different periods will allow you to discover trends. Go to Appendix C. If you are using a TI-83 Plus, you can download the program and data sets and run the application as directed. Press the APPS key on your calculator, then choose the application CHEMAPPS. Press 8, then highlight ALL on the screen, press 1, then highlight LOAD and press 2 to load the data into your calculator. Quit the application, and then run the program RADIUS. For Atomic radius (pm) Atomic Radii of Main-Block Elements 250 200 150 100 50 0 Cs Rb K Na Li H 1 2 13 1 15 16 17 18 Group number Period 6 Period 5 Period Period 3 Period 2 He Period 1 L 1, press 2nd and LIST, and choose ATNUM. For L 2, press 2nd and LIST and choose ATRAD. If you are using another calculator, your teacher will provide you with keystrokes and data sets to use. a. Would you expect any atomic number to have an atomic radius of 20 pm? Explain. b. A relationship is considered a function if it can pass a vertical line test. That is, if a vertical line can be drawn anywhere on the graph and only pass through one point, the relationship is a function. Does this set of data represent a function? Explain. c. How would you describe the graphical relationship between the atomic numbers and atomic radii? Chapter Test Chapter Resource File 153 REVIEW ANSWERS b. A nonmetal of low reactivity in Group 18, it has a filled outer-energy level, so there is little tendency to lose, gain, or share electrons. c. A reactive metal in Group 1, it has a low ionization energy because the loss of an electron to form a positive ion gives it a noble-gas configuration. 6. Argon has a complete energy level of electrons, and therefore is not reactive. Chlorine s electron configuration is one short of a full shell, so it has a tendency to react with elements from which it can gain one electron. Potassium has only a single valence electron, so it readily reacts to lose that electron. 7. Elements were first classified by reactivity and atomic mass. The modern periodic table has trends of atomic size, electron configuration, ionization energy, and electron affinity, among other factors not covered in this chapter. 8. Groups 1 and 2 have the same number of valence electrons as their group number. Groups 13 18 have n 10 valence electrons, n being the group number. 9. Element A is more likely to lose an electron and become a cation because it has a lower ionization energy. 50. As a noble gas with a full valence shell, 3s 2 3p 6, argon is unreactive. Chlorine has one less electron than argon, 3s 2 3p 5, so it tends to react by gaining one electron to form an anion with a 1 charge. Potassium has one more electron than argon, 3s 2 3p 6 s 1, so it tends to react by losing one electron to form a cation with a 1+ charge. Answers on p. 155A B Chapter The Periodic Table 153
STANDARDIZED TEST PREP STANDARDIZED TEST PREP uestion 3 Choice C is the corect answer because the stable tructure of noble gases means that t takes more energy to remove lectrons. Choices A and B are rong because noble gases have elatively small radii and low elecron affinities. Choice D is incorect because noble gases do not orm either anions or cations. uestion 5 Filling in the gaps emonstrated the predictive value f the table. That it could be used o determine the properties of eleents not known to exist suported the system of classification sed in the table. uestion 8 The correct answer is. Beryllium and strontium are in he same column, so they have the ame valence electron arrangeent. Although boron and berylium are close together, they have ifferent numbers of valence elecrons that determine the element's roperties. uestion 10 Properties are based n electron structure, which is the rganizing principle of the olumns. Electron structure varies cross the rows of the table, but he electron structure is the same n each column. Properties of the lement indicate its column but ot its row. 15 UNDERSTANDING CONCEPTS Directions (1 ): For each question, write on a separate sheet of paper the letter of the correct answer. 1 2 3 Which of the following elements is formed in stars? A. curium C. gold B. einsteinium D. mendelevium Why are the Group 17 elements, the halogens, the most reactive of the nonmetal elements? F. They have the largest atomic radii. G. They have the highest ionization energies. H. They are the farthest right on the periodic table. I. They require only one electron to fill their outer energy level. Which of the following is a property of noble gases as a result of their stable electron configuration? A. large atomic radii B. high electron affinities C. high ionization energies D. a tendency to form both cations and anions Which of these is a transition element? F. Ba H. Fe G. C I. Xe Directions (5 7): For each question, write a short response. 5 6 How did the discovery of the elements that filled the gaps in Mendeleev s periodic table increase confidence in the periodic table? Why is iodine placed after tellurium on the periodic table if the atomic mass of tellurium is less than that of iodine? 7 What is the outermost occupied energy level in atoms of the elements in Period? READING SKILLS Directions (8 10): Read the passage below. Then answer the questions. 8 9 0 The atomic number of beryllium is one less than that of boron, which follows it on the periodic table. Strontium, which is directly below beryllium in period 5 of the periodic table has 3 more protons and 3 more electrons than beryllium. However, the properties of beryllium resemble the much larger strontium more than those of similar-sized boron. The properties of beryllium are more similar to those of strontium than those of boron because A. A strontium atom is larger than a boron atom. B. Strontium and beryllium are both reactive nonmetals. C. A strontium atom has more electrons than a boron atom. D. Strontium has the same number of valence electrons as beryllium. Beryllium and strontium are both located in the second column of the periodic table. To which of these classifications do they belong? F. alkali metals G. alkaline earth metals H. rare earth metals I. transition metals Why is it easier to determine to which column of the periodic table an element belongs than to determine to which row it belongs, based on observations of its properties? 5 Chapter The Periodic Table Answers 1. C 2. I 3. C. H 5. The gaps were significant because they predicted the properties of new elements that would be discovered. Their discovery demonstrated that the table was a useful tool for organizing information about atoms. 6. Because the periodic table is based on atomic number, not atomic mass. The atomic number of iodine is one higher than the atomic number of tellurium. 7. Level 8. D 9. G 10. It is easier to determine the column because all the elements in a column have the same outer electron structure and, therefore, similar properties. Properties of elements across a row of the table vary widely. 11. D 12. G 13. Ionization energy tends to increase from left to right across the table because elements have increasingly more protons so the attraction on the outer electrons is stronger.