hapter 3: Electronic Structure and the Periodic Law HPTER OUTLINE 3.1 The Periodic Law and Table 3.2 Electronic rrangements in toms 3.3 The Shell Model and hemical Properties 3.4 Electronic onfigurations 3.5 nother Look at the Periodic Table 3.6 Property Trends within the Periodic Table LERNING OJETIVES/SSESSMENT When you have completed your study of this chapter, you should be able to: 1. Locate elements in the periodic table on the basis of group and period designations. (Section 3.1; Exercise 3.4) 2. etermine the number of electrons in designated atomic orbitals, subshells, or shells. (Section 3.2; Exercise 3.12) 3. etermine the number of valence shell electrons and the electronic structure for atoms, and relate this information to the location of elements in the periodic table. (Section 3.3; Exercises 3.18 and 3.22) 4. etermine the following for elements: the electronic configuration of atoms, the number of unpaired electrons in atoms, and the identity of atoms based on provided electronic configurations. (Section 3.4; Exercises 3.24 and 3.28) 5. etermine the shell and subshell locations of the distinguishing electrons in elements, and based on their location in the periodic table, classify elements into the categories given in Figures 3.10 (representative element, transition element, inner transition element, noble gas) and 3.12. (metal, metalloid, nonmetal). (Section 3.5; Exercises 3.34 and 3.36) 6. Recognize property trends of elements within the periodic table, and use the trends to predict selected properties of the elements. (Section 3.6; Exercises 3.40 and 3.42) LETURE HINTS N SUGGESTIONS 1. Extend the concept of chemical change and chemical properties to the atomic level. hemical changes cause a change in the constituent particles. The atoms are rearranged to make different constituent particles. This rearrangement involves the electrons of the atoms. Thus, atoms with similar chemical properties must have similar electronic arrangements. 2. Relate the arrangement of the periodic table with groups and periods to the electronic structure of the atom, and the filling order of the orbitals. This facilitates the understanding of the ʺouter electronsʺ determining the chemical combinations. 3. void bringing in any detailed discussion about nuclear changes (covered in hapter 10) into this chapter. Mention that isotopes are either stable or radioactive (unstable) as well as the facts that only nuclear reactions involve nuclear changes and that all other chemical reactions involve electrons, but defer any further discussion of radioactivity until the later chapter. 4. If samples of some of the elements are available, showing them may benefit the discussion of the periodic table as it relates to metals, non metals, similarity within groups, etc. SOLUTIONS FOR THE EN OF HPTER EXERISES THE PERIOI LW N TLE (SETION 3.1) 3.1 Group Period a. a II (2) 4 b. element number 22 IV (4) 4 53
54 hapter 3 Group Period c. nickel VIII (10) 4 d. tin IV (14) 5 3.2 Group Period a. element number 27 VIII (9) 4 b. Pb IV (14) 6 c. arsenic V (15) 4 d. a II (2) 6 3.3 Symbol Name a. elongs to group VI(16) and period 3 S sulfur b. The first element (reading down) in group VI(6) r chromium c. The fourth element (reading left to right) in period 3 Si silicon d. elongs to group I(11) and period 5 g silver 3.4 Symbol Name a. The noble gas belonging to period 4 Kr krypton b. The fourth element (reading down) in group IV (14) Sn tin c. elongs to group VI (6) and period 5 Mo molybdenum d. The sixth element (reading left to right) in period 6 Nd neodymium 3.5 a. How many elements are located in group VIII(8,9,10) of the periodic table? 12 b. How many elements are found in period 2 of the periodic table? 8 c. How many total elements are in group II(2) and VI(16) of the periodic table? 11 3.6 a. How many elements are located in group VII (17) of the periodic table? 5 b. How many total elements are found in periods 2 and 3 of the periodic table? 16 c. How many elements are found in period 6 of the periodic table? 32 3.7 a. This is a vertical arrangement of elements in the periodic table group b. The chemical properties of the elements repeat in a regular way as periodic law the atomic numbers increase c. The chemical properties of elements 11, 19, and 37 demonstrate this periodic law principle d. Elements 4 and 12 belong to this arrangement group 3.8 a. This is a horizontal arrangement of elements in the periodic table. period b. Element 11 begins this arrangement in the periodic table. period c. The element nitrogen is the first member of this arrangement. group d. Elements 9, 17, 35, and 53 belong to this arrangement. group ELETRONI RRNGEMENTS IN TOMS (SETION 3.2) 3.9 ccording to ohr theory, an electron in an orbit located farther from the nucleus would have higher energy than an electron in an orbit close to the nucleus. 3.10 Protons are subatomic particles with a positive charge that are located in the nucleus.
Electronic Structure and the Periodic Law 55 3.11 a. 2s orbital 2 electrons b. 2s subshell 2 electrons c. The first shell 2 electrons 3.12 a. 2p orbital 2 electrons b. 2p subshell 6 electrons c. The second shell 8 electrons 3.13 Nine (9) orbitals are found in the third shell: one 3s orbital, three 3p orbitals, and five 3d orbitals. 3.14 Sixteen (16) orbitals are found in the second shell: one 4s orbital, three 4p orbitals, five 4d orbitals, and seven 4f orbitals. 3.15 Five (5) orbitals are found in the 3d subshell. The maximum number of electrons that can be located in this subshell is 10 because each of the five orbitals can hold two electrons. 3.16 Seven (7) orbitals are found in a 4f subshell. The maximum number of electrons that can be located in this subshell is 14 because each of the seven orbitals can hold two electrons. 3.17 The subshells in the fourth shell are 4s, 4p, 4d, 4f. The maximum number of electrons in each subshell are 2 (4s), 6 (4p), 10 (4d), and 14 (4f). The total number of electrons that can occupy the fourth shell is 32. THE SHELL MOEL N HEMIL PROPERTIES (SETION 3.3) 3.18 a. element number 54 8 electrons b. The first element (reading down) in group V (15) 5 electrons c. Sn 4 electrons d. The fourth element (reading left to right) in period 3 4 electrons 3.19 a. element number 35 7 electrons b. Zn 2 electrons c. strontium 2 electrons d. The second element in group V(15) 5 electrons 3.20 esium is the period 6 element with chemical properties most like sodium. esium has 1 valence shell electron. Sodium also has only 1 valence shell electron. 3.21 The period 5 element with chemical properties most like silicon is tin (Sn). Tin has four valence shell electrons. Silicon also has four valence shell electrons. 3.22 I would expect to find silver and gold in addition to the copper because these elements are all in the same group on the periodic table. Elements that are in the same group have similar chemical properties; therefore, if copper is part of this ore, then the other elements that are most similar to it are also likely to be part of the ore. 3.23 Strontium would be likely to be deposited in bones because it is in group II(2), just like calcium (a major component of bone).
56 hapter 3 ELETRONI ONFIGURTIONS (SETION 3.4) 3.24 Electron onfiguration Unpaired Electrons a. element number 37 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 1 1 b. Si 1s 2 2s 2 2p 6 3s 2 3p 2 2 Electron onfiguration Unpaired Electrons c. titanium 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 2 2 d. r 1s 2 2s 2 2p 6 3s 2 3p 6 0 3.25 Electron onfiguration Unpaired Electrons a. r 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 5 1 b. element number 36 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 0 c. cadmium 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 0 d. Sb 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 3 3 3.26 Electron onfiguration Solutions a. s electrons in magnesium 1s 2 2s 2 2p 6 3s 2 6 b. unpaired electrons in nitrogen 1s 2 2s 2 2p 3 3 c. filled subshells in l 1s 2 2s 2 2p 6 3s 2 3p 1 4 3.27 Electron onfiguration Solutions a. total electrons in Ge have a number designation (before the letters) of 4 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 2 4 b. unpaired p electrons in sulfur, number designation of the unpaired electrons 1s 2 2s 2 2p 6 3s 2 3p 4 2 electrons, number designation = 3 c. 3d electrons in tin 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 2 10 3.28 Symbol Name a. ontains only two 2p electrons carbon b. ontains an unpaired 3s electron Na sodium c. ontains two unpaired 3p electrons Si or S silicon or sulfur d. ontains three 4d electrons Nb niobium e. ontains three unpaired 3d electrons V or o vanadium or cobalt 3.29 Symbol Name a. ontains one unpaired 5p electron In or I indium or iodine b. ontains a half filled 5s subshell Rb rubidium c. ontains a half filled 6p subshell i bismuth d. The last electron completes the 4d d cadmium subshell e. The last electron half fills the 4f subshell Eu europium 3.30 a. selenium [r]4s 2 3d 10 4p 4 c. a [r]4s 2 b. element number 23 [r]4s 2 3d 3 d. carbon [He]2s 2 2p 2
Electronic Structure and the Periodic Law 57 3.31 a. lead [Xe]6s 2 4f 14 5d 10 6p 2 c. n element [r]4s 2 3d 4 that contains 24 electrons b. element number 53 [Kr]5s 2 4d 10 5p 5 d. silicon [Ne]3s 2 3p 2 3.32 a. sodium [Ne]3s 1 e. phosphorus [Ne]3s 2 3p 3 b. magnesium [Ne]3s 2 f. sulfur [Ne]3s 2 3p 4 c. aluminum [Ne]3s 2 3p 1 g. chlorine [Ne]3s 2 3p 5 d. silicon [Ne]3s 2 3p 2 h. argon [Ne]3s 2 3p 6 3.33 Eighteen (18) elements have the symbol [Kr] in their abbreviated electronic configurations. NOTHER LOOK T THE PERIOI TLE (SETION 3.5) 3.34 a. nickel d area 3.35 a. Kr p area b. Rb s area b. tin p area c. element 51 p area c. Pu f area d. m f area d. element 40 d area 3.36 a. iron transition b. element 15 representative c. U inner transition d. xenon noble gas e. tin representative 3.38 a. element 51 metalloid b. iodine nonmetal c. l metal d. radon nonmetal e. Pt metal 3.37 a. W transition b. m inner transition c. element 10 noble gas d. helium noble gas e. barium representative 3.39 a. rubidium metal b. arsenic metalloid c. element 50 metal d. S nonmetal e. r nonmetal PROPERTY TRENS WITHIN THE PERIOI TLE (SETION 3.6) 3.40 a. Na or Mg Na more metallic 3.41 a. or Sn Sn more metallic b. Pb or Ge Pb b. Sb or In In c. Mg or a a c. a or s a d. s or Li s d. l or Mg Mg 3.42 a. Ga or Se Ga larger radius b. N or Sb Sb c. O or d. Te or S Te 3.43 a. Mg or Sr Sr larger radius b. Rb or a Rb c. S or Te Te d. I or Sn Sn 3.44 a. Li or K K loses e more easily b. or Sn Sn c. Mg or S Mg d. Li or N Li 3.45 a. Mg or l Mg loses e more easily b. a or e a c. S or l l d. Te or O Te ITIONL EXERISES 3.46 hemical properties are dependent on the number of valence electrons an atom contains, not the number of neutrons an atom contains; therefore, the chemical properties of isotopes of the
58 hapter 3 same element are the same because all isotopes of the same element contain the same number of electrons, including valence electrons. 3.47 Mercury and bromine share the physical property of being liquids at room temperature. They are not in the same group, though, because their chemical properties differ. 3.48 The atom with the electron configuration of 1s 2 2s 2 2p 4 is oxygen, which has an atomic weight of 16.00 u; therefore, the mass of 3.0 x 10 20 oxygen atoms is 8.0 mg. 20 3.0 10 atoms O 16.00 u 24 1.661 10 g 1000 mg = 8.0 mg 1atomO 1u 1g 16.00 g O 20 1000 mg or 3.0 10 atoms O = 8.0 mg 23 6.022 10 atoms O 1g 3.49 The density of the metallic elements increases from left to right across a period of the periodic table because as the mass slowly increases, the volume rapidly decreases across the period; therefore, the density must increase because a larger mass is divided by a smaller volume. 3.50 grams 10.02 g grams Molar Mass = = = 40.08 mole 0.250 moles mole The element is calcium, which is a representative element that conducts electricity. LLIE HELTH EXM ONNETION 3.51 The arrangement of the modern periodic table is based on atomic (b) number. 3.52 The horizontal row of the periodic table are called (d) periods. 3.53 (c) Nickel is an example of a transition element. 3.54 (d) Mg and a have similar chemical properties because they are part of the same group II (2). 3.55 (b) luminum is not a semimetal; it is a metal. 3.56 Nonmetals are located on the (a) upper right of the periodic table. 3.57 The number 36 on the periodic table entry for krypton represents the (a) atomic number. 3.58 (b) Sodium is an alkali metal; it belongs to group I. 3.59 (b) Mg is an alkaline earth metal. 3.60 The maximum number of electrons that each p orbital can hold is (b) 2. 3.61 (a) K is larger than r. 3.62 The element with the smallest atomic radius is (b) Mg. The order of increasing atomic radius is magnesium, strontium, barium, radium.
Electronic Structure and the Periodic Law 59 3.63 Ionization energy is (a) the energy required to completely remove an electron from an atom or ion. 3.64 (d) Sr has the largest first ionization energy. 3.65 (a) Metals conduct electricity. 3.66 (d) Valence describes the electrons in the outermost principal energy level of an atom. 3.67 If the electron configuration of an element is written 1s 2 2s 2 2p 6 3s 1, the element s atomic (a) number is 11. 3.68 (a) Na/K have the same number of electrons in their outermost energy level. They both have 1 valence electron. 3.69 The number of unpaired electrons in the outer subshell of a phosphorus atom (atomic number: 15) is (c) 3. 3.70 (b) 2 valence electrons are needed to complete the outer valence shell of sulfur. 3.71 n atom that has five 3p electrons in its ground state is (c) chlorine. HEMISTRY FOR THOUGHT 3.72 alcium bromide is ar2 and strontium bromide is Srr2, because calcium and strontium have the same number of valence electrons as magnesium, which forms Mgr2 when it reacts with bromine. 3.73 statine is probably a dark color and has a metallic sheen. It is likely a solid under normal conditions. Fluorine is probably a lighter color than the yellow green of chlorine. It is likely a gas under normal conditions. statine is the halogen that follows iodine on the periodic table and is likely to have properties most similar to iodine. Fluorine is the halogen that precedes chlorine on the periodic table and is likely to have properties most similar to chlorine. 3.74 Gold, silver, copper, nickel, platinum, and zinc are used in coins and medals because they have limited chemical reactivity, they are malleable, and they have low enough melting points to be melted and poured into uniform shapes. Gold is useful in electrical connectors for critical electronic parts such as computers in space craft because it not only conducts electricity, but also has limited chemical reactivity, which means it can be trusted to continue to conduct electricity without undergoing a chemical change. 3.75 Since calcium is more reactive towards water than magnesium, the trend is expected to continue down the group. Strontium and barium most likely react more vigorously with cold water than calcium does. Sr + 2 H2O Sr(OH)2 + H2 a + 2 H2O a(oh)2 + H2
60 hapter 3 3.76 The number of floors in Hotel Five is 5 and the number of rooms on the top floor of Hotel Five is 9. Each hotel has the same number of floors as the hotel number. The number of rooms on each floor is an increasing odd integer (1, 3, 5, 7). 3.77 If zirconium metal is produced from a raw material, then titanium and hafnium are also likely to be produced from the same raw material. ll of these elements are part of the same group and share chemical properties. EXM QUESTIONS MULTIPLE HOIE 1. Which of the following elements is found in the same period of the periodic table period as Sn? a. Si c. Te b. s d. more than one response is correct 2. Which element is the first one in the group IV (14) of the periodic table? a. b. Na c. Sc d. Ti 3. What is the symbol of the element that is in Period 4, and Group II (2) of the periodic table? a. Zn b. a c. d. Ti 4. Silver, g, belongs to what period of the periodic table? a. I b. 2 c. 5 d. 12 5. If the formula for hydrosulfuric acid is H2S, what would be the expected formula for the compound between hydrogen and tellurium, Te? a. HTe b. HTe2 c. H2Te d. cannot be determined 6. Which of the following statements applies to p subshells? a. The p subshell can contain a maximum of 14 electrons. b. The p subshell is subdivided into three perpendicular shapes. c. The p subshell fills with 2 electrons in the first subdivision, then 2 in the next, etc. d. ll of these statements are correct with reference to p subshells. 7. Which of the following subshells has the highest energy? a. 4s b. 4p c. 4d d. 4f
8. Suppose an electron moved from the second shell to the third shell. a. The move required an input of energy. b. The move gave off energy. c. Electrons can move spontaneously from shell to shell. d. Electrons canʹt move from shell to shell, but can move into the nucleus. 9. The total number of f orbitals in an f subshell is: a. 2. b. 5. c. 7. d. 10. Electronic Structure and the Periodic Law 61 10. The maximum number of electrons that can occupy a 3d subshell is: a. 2. b. 4. c. 6. d. 10. 11. The maximum number of electrons that can occupy a 4p subshell is: a. 2. b. 4. c. 6. d. 10. 12. What is the maximum number of electrons that can occupy the third shell? a. 2 b. 10 c. 18 d. 32 13. How many electrons are in the outer shell of element 15? a. 15 b. 5 c. 3 d. 2 14. Which of the following elements should have properties similar to those of nitrogen (element 7)? a. b. Si c. P d. O 15. Which of the following has the same number of outer shell electrons as sulfur, S? a. b. O c. N d. F 16. What is the shell number for the outer shell electrons in bromine, r? a. 3 b. 4 c. 5 d. 6 17. Which of the following elements has an electronic configuration of 1s 2 2s 2 2p 6 3s 2 3p 1? a. F b. l c. Mg d. Ga 18. The total number of unpaired electrons in silicon, Si, is: a. 0. b. 1. c. 2. d. 3.
62 hapter 3 19. Which of the following contains the same number of unpaired electrons as potassium (K)? a. Sc c. Mg b. l d. more than one response is correct 20. Which of the following will not have electrons in the third shell? a. K b. Mg c. Na + d. g + 21. Which of the following pairs have the same number of electrons in the valence shell? a. K and a b. S 4+ and l 3+ c. Na + and Ne d. Ne and He 22. The electronic configuration of element 17 ends with: a. 2p 3. b. 3p 5. c. 2p 5. d. 3p 3. 23. Which of the following elements contains a total of 10 ʺsʺ electrons? a. Sr c. s b. Ne d. more than one response is correct 24. What type of electron is the distinguishing electron in S? a. s b. p c. d d. f 25. Which of the following distinguishing electrons represents an element with properties similar to an element with a 3p 3 distinguishing electron? a. 4p 3 b. 3p 2 c. 3d 3 d. 2p 2 26. Which element is represented by the distinguishing electron configuration 3d 8? a. Ni b. u c. Pd d. g 27. Which of the following elements is most likely to be a metalloid? a. Ge b. Mo c. S d. s 28. Metalloids can express the characteristics of both metals and nonmetals. Which of the elements below is more likely to have the characteristics of a metal than a nonmetal? a. s b. Se c. Si d. Sb 29. In which of the following elements is the distinguishing electron in a d orbital? a. r b. O c. Kr d. Sr
Electronic Structure and the Periodic Law 63 30. Which of the following elements is classified as a transition element? a. element 76 b. element 60 c. element 56 d. element 17 31. Which of the following elements is classified as a representative metal? a. element 30 b. element 26 c. element 38 d. element 63 32. Which of the following elements is a nonmetal? a. Ni b. u c. a d. I 33. Which one of these elements is a gas at room temperature? a. antimony b. phosphorus c. nitrogen d. arsenic 34. Which element has the distinguishing electron, 5p 4? a. r b. Mn c. Te d. Kr 35. The radius of a K atom is a a atom. a. smaller than b. larger than c. equal to d. inverted from 36. The melting point of oxygen is selenium, Se. a. lower than b. higher than c. equal to d. inverted from 37. Which of the following is a noble gas? a. gold b. platinum c. neon d. chlorine 38. The symbol of the element in period 2, group III (13) is: a. Mg. b. e. c. l. d.. 39. Which element is used for relieving the symptoms of a cold? a. u b. K c. Zn d. Fe 40. Which of the following statements conforms to the trends within the Periodic Table of the Elements? a. Elements become more likely to be gases at the bottom of a group. b. Elements become more likely to be a solid at the bottom of a group. c. Elements become more likely to be darkly colored at the bottom of a group. d. Elements become more likely to be more brittle at the bottom of a group.
64 hapter 3 41. The highest energy shell of an element that contains electrons is know as the: a. subshell. b. atomic orbital. c. valence shell. d. none of these 42. states that, electrons will not join other electrons in an orbital if an empty orbital of the same energy is available. a. Hund s rule c. Periodic law b. Pauli exclusion principle d. None of these 43. explains why orbitals can contain a maximum of two electrons. a. Hund s rule c. Periodic law b. Pauli exclusion principle d. None of these 44. hoose the correct electronic configuration for arsenic, s. a. [r] 4s 2 3d 10 4p 3 c. [r] 4s 2 4d 10 4p 3 b. 4s 2 3d 10 4p 3 d. 4s 2 4d 10 4p 3 45. Which element has the largest atomic radius? a. I b. F c. Li d. s 46. The noble gases is the family name for which group of the periodic table? a. V (15) b. VI (16) c. VII (17) d. VIII (18) 47. Which of the following groups belongs to the transition elements? a. 1 (1) b. II (2) c. III (3) d. III (13) 48. Which of the following is a reasonable explanation as to why atomic radii become smaller as one moves to the right for the representative elements in a period? a. The charge of the nucleus increases, pulling the electron cloud closer. b. More densely packed shells are always smaller. c. Elements become less metallic. d. tomic radii actually increase from left to right in a period. TRUE FLSE 1. The fifth period begins with Rb. T 2. 3d orbital can hold 6 electrons. F
3. Tin (Sn) is a representative element. T Electronic Structure and the Periodic Law 65 4. The electron configuration for each shell starts with an s subshell. T 5. ll of the transition elements are metals. T 6. Sodium, Na, and potassium, K, are in the same period. F 7. The radius of a magnesium atom is larger than the radius of a sodium atom. F 8. The magnesium atom loses an electron more easily than a calcium atom. F 9. The distinguishing electron in antimony, Sb, is 5p 3. T 10. The fourth shell contains four subshells. T 11. The second shell has a maximum capacity of 6 electrons. F 12. Element number 92, uranium, U, is a metal. T 13. rgon completes the fourth period of the periodic table. F 14. Hydrogen is a noble gas. F 15. bromine atom has a larger radius than a chlorine atom. T 16. bromine atom has a larger first ionization energy than a chlorine atom. F 17. Sulfur has a metallic luster. F 18. The distinguishing electron for most non metals is an s electron. F 19. Tin (Sn), which is found in Group IV (14), has four electrons in the outside shell. T
66 hapter 3 20. Moving across the 4th period from left to right, the valence electrons go into the same shell, and the atomic radius decreases. The decrease in atomic radius is due to the increase in the attraction of the nucleus for the electrons in the shells. T