CHAPTER 10 MODERN ATOMIC THEORY AND THE PERIODIC TABLE SOLUTIONS TO REVIEW QUESTIONS 1. An electron orbital is a region in space around the nucleus of an atom where an electron is most probably found. 2. A second electron may enter an orbital already occupied by an electron if its spin is opposite that of the electron already in the orbital and all other orbitals of the same sublevel contain an electron. 3. The valence shell is the outermost energy level of an atom. 4. Valence electrons are the electrons located in the outermost energy level of an atom. Valence electrons are involved in bonding. They are important because information involves the gain or loss of valence electrons. Covalent bonding involves sharing valence electrons. 5. All the electrons in the atom are located in the orbitals closest to the nucleus. 6. Both 1s and 2s orbitals are spherical in shape and located symmetrically around the nucleus. The sizes of the spheres are different the radius of the 2s orbital is larger than the 1s. The electrons in 2s orbitals are located further from the nucleus. 7. The letters used to designate the energy sublevels are s, p, d, and f. 8. 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p. 9. s 2 electrons per shell p 6 electrons per shell after the first energy level d 10 electrons per shell after the second energy level. 10. The main difference is that the Bohr orbit has an electron traveling a specific path around the nucleus while an orbital is a region in space where the electron is most probably found. 11. Bohr s model was inadequate since it could not account for atoms more complex than hydrogen. It was modified by Schr odinger into the modern concept of the atom in which electrons exhibit wave and particle properties. The motion of electrons is determined only by probability functions as a region in space, or a cloud surrounding the nucleus. 12. s orbital. - 105 -
p orbitals Px z Py z Pz z x x x y y 13. 4 is the fourth principal energy level f indicates the energy sublevel 3 indicates the number of electrons in the f sublevel 14. Ir, Zr, and Ag are not representative elements; they are transition elements. 15. Elements in the p-block all have one to six electrons in the p sublevel. 16. Atomic # Symbol 6 C 7 N 8 O 15 P 33 As Elements with atomic numbers 7, 15, and 33 are all in the same group on the periodic table. They have an outermost electron structure of s 2 p 3. 17. The first three elements that have six electrons in their outermost energy level are O, S, and Se. 18. The greatest number of elements in any period is 32. The 6 th period has this number of elements. 19. The elements in Group A always have their last electrons in the outermost energy level, while the last electrons in Group B lie in an inner level. 20. Pairs of elements which are out of sequence with respect to atomic masses are: Ar and K; Co and Ni; Te and I; Th and Pa; U and Np; Pu and Am; Lr and Rf; Sg and Bh. 21. Dimitri Mendeleev, of Russia and Lothar Meyer, of Germany both independently published results that led to the current periodic table. 22. Dimitri Mendeleev is credited with being the father of the modern periodic table. - 106 -
SOLUTIONS TO EXERCISES 1. Element Total Electrons Valence Electrons (a) Li 3 1 Mg 12 2 (c) Ca 20 2 (d) F 9 7 2. Element Total Electrons Valence Electrons (a) Na 11 1 As 33 5 (c) P 15 5 (d) Al 13 3 3. Electron configurations (a) Sc 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 1 Cs 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d l0 5p 6 6s l (c) Br 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 5 (d) O 1s 2 2s 2 2p 4 4. (a) Mn 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 5 Ar 1s 2 2s 2 2p 6 3s 2 3p 6 (c) Ga 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 p 1 (d) N 1s 2 2s 2 2p 3 5. The spectral lines of hydrogen are produced by energy emitted when the electron from a hydrogen atom, which has absorbed energy, falls from a higher energy level to a lower energy level (closer to the nucleus). 6. Bohr said that a number of orbits were available for electrons, each corresponding to an energy level. When an electron falls from a higher energy orbit to a lower energy orbit, energy is given off as a specific wavelength of light. Only those energies in the visible range are seen in the hydrogen spectrum. Each line corresponds to a change from one orbit to another. 7. 16 orbitals in the 4 th principal energy level; 1 in s, 3 in p, 5 in d, and 7 in f. The s and p orbitals are in the 4 th period, the d orbitals are in the 5 th period and the f orbitals are in the 6 th period. 8. 18 electrons in third energy level; 2 in s, 6 in p, 10 in d - 107 -
9. (a) 14 7 N 35 17 Cl (c) 65 30 Zn (d) 91 40 Zr 127 53 I 10. (a) 28 14 Si 32 16 S (c) 40 18 Ar (d) 51 23 V 31 15 P 11. (a) O 1s 2 2s 2 2p 4 Ca 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 (c) Ar 1s 2 2s 2 2p 6 3s 2 3p 6 (d) Br 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 5 Fe 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 12. (a) Li 1s 2 2s 1 P 1s 2 2s 2 2p 6 3s 2 3p 3 (c) Zn 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 (d) Na 1s 2 2s 2 2p 6 3s 1 K 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1-108 -
13. (a) fluorine, F sodium, Na (c) sulfur, S (d) nickel, Ni 14. (a) boron, B silicon, Si (c) lead, Pb (d) tellurium, Te 15. Atomic No. Electron Configuration Abbreviated (a) 49 (In) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 1 [Kr] 5s 2 4d 10 5p 1 18(Ar) 1s 2 2s 2 2p 6 3s 2 3p 6 [Ar] (c) 5 (B) 1s 2 2s 2 2p 1 [He] 2s 2 2p 1 (d) 3 (Li) 1s 2 2s 1 [He] 2s 1 50 (Sn) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 2 [Kr] 5s 2 4d 10 5p 2 (f) 30 (Zn) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 [Ar] 4s 2 3d 10 16. (a) 19 (K) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 [Ar] 4s 1 26 (Fe) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 [Ar] 4s 2 3d 6 (c) 38 (Sr) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 [Kr] 5s 2 (d) 34 (Se) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 4 [Ar] 4s 2 3d 10 4p 4 12 (Mg) 1s 2 2s 2 2p 6 3s 2 [Ne] 3s 2 (f) 48(Cd) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 [Kr] 5s 2 4d 10 17. (a) Titanium (Ti) (c) Argon (Ar) Arsenic (As) (d) Bromine (Br) Manganese (Mn) 18. (a) Phosphorus (P) Zinc (Zn) (c) Calcium (Ca) - 109 -
(d) Selenium (Se) Potassium (K) 19. (a) F (c) S Co (d) Kr Ru 20. (a) Cl (c) Mg Ni (d) Cu Ba 21. (a) 32 60 16S 28 Ni 22. (a) 13p 14n 2e 8e 3e 27 13 Al 22p 26n 2e 8e 8e 4e 48 22 Ti 23. The eleventh electron of sodium is located in the third energy level because the first and second levels are filled. Also the properties of sodium are similar to the other elements in Group 1A. - 110 -
24. The last electron in potassium is located in the fourth energy level because the 4s orbital is at a lower energy level than the 3d orbital. Also the properties of potassium are similar to the other elements in Group 1A. 25. Noble gases all have filled s and p orbitals in the outermost energy level. 26. Noble gases each have filled s and p orbitals in the outermost energy level. 27. Moving from left to right in any period of elements, the atomic number increases by one from one element to the next and the atomic radius generally decreases. Each period (except period 1) begins with an alkali metal and ends with a noble gas. There is a trend in properties of the elements changing from metallic to nonmetaliic from the beginning to the end of the period. 28. The elements in a group have the same number of outer energy level electrons. They are located vertically on the periodic table. 29. (a) 4 6 (c) 1 (d) 7 3 30. (a) 5 5 (c) 6 (d) 2 3 31. The outermost energy level contains one electron in an s orbital. 32. All of these elements have a s 2 d 10 electron configuration in their outermost energy levels. 33. (a) and (g) and (d) 34. (a) and (f) and (h) 35. 12, 38 since they are in the same periodic group. 36. 7, 33 since they are in the same periodic group. 37. (a) K, metal (c) S, nonmetal Pu, metal (d) Sb, metalloid 38. (a) I, nonmetal (c) Mo, metal W, metal (d) Ge, metalloid 39. Period 6, lanthanide series, contains the first element with an electron in an f orbital. 40. Period 4 Group 3B contains the first element with an electron in a d orbital. 41. Group 7A contain 7 valence electrons. Group 7B contain 2 electrons in the outermost level and 5 electrons in an inner d orbital. Group A elements are representative while Group B elements are transition elements. - 111 -
42. Group 3A contain 3 valence electrons. Group 3B contain 2 electrons in the outermost level and one electron in an inner d orbital. Group A elements are representative while Group B elements are transition elements. 43. The valence energy level of an atom can be determined by looking at what period the element is in. Period 1 corresponds to valence energy level 1, period 2 to valence energy level 2 and so on. The number of valence electrons for element s 1 18 can be determined by looking at the group number. For example, boron is under Group 3A, therefore it has three valence shell electrons. 44. (a) Mg 1s 2 2s 2 2p 6 3s 2 P 1s 2 2s 2 2p 6 3s 2 3p 3 (c) K 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 (d) F 1s 2 2s 2 2p 5 Se 1s 2 2s 2 2p 6 3s 2 3p 6 3d 4s 2 10 4p 6 (f) N 1s 2 2s 2 2p 3 45. (a) Na þ, (d) F and Ne have 8 valence electrons. 46. (a) 7A, Halogens (d) 8A, Noble Gases 2A, Alkaline Earth Metals 8A, Noble Gases (c) 1A, Alkali Metals (f) 1A, Alkali Metals 47. (a) The four most abundant elements in the earth s crust, seawater, and air are: O: 1s 2 2s 2 2p 4 Si: 1s 2 2s 2 2p 6 3s 2 3p 2 Al: 1s 2 2s 2 2p 6 3s 2 3p 1 Fe: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 The five most abundant elements in the human body are: O: 1s 2 2s 2 2p 4 C: 1s 2 2s 2 2p 2 H: 1s 1 N: 1s 2 2s 2 2p 3 Ca: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 48. Maximum number of electrons (a) Any orbital can hold a maximum of two electrons. A d sublevel can hold a maximum of ten electrons. (c) The third principal energy level can hold two electrons in 3s, six electrons in 3p, and ten electrons in 3d for a total of eighteen electrons. (d) Any orbital can hold a maximum of two electrons. An f sublevel can hold a maximum of fourteen electrons. 49. Name of elements (a) Magnesium Phosphorus (c) Argon 50. Nitrogen has more valence electrons on more energy levels. More varied electron transitions are possible. 51. 1:5 1:5 108 ¼ 150,000,000 ¼ 8 1:0 10 1-112 -
52. (a) Ne Ge (c) F (d) N 53. The outermost electron structure for the elements in 7A is s 2 p 5. 54. Transition elements are found in Groups 1B 8B, lanthanides and actinides. 55. In transition elements the last electron added is in a d or f orbital. The last electron added in a representative element is in an s or p orbital. 56. Elements 7, 15, 33, 51, and 83 all have 5 electrons in their valence shell. 57. Family names (a) Alkali Metals Alkaline Earth Metals (c) Halogens 58. Sublevels (a) sublevel p sublevel d (c) sublevel f 59. (a) Na representative element metal N representative element nonmetal (c) Mo transition element metal (d) Ra representative element metal As representative element metalloid (f) Ne noble gas nonmetal 60. If element 36 is a noble gas, 35 would be in periodic Group 7A and 37 would be in periodic Group 1A. 61. Answers will vary but should at least include a statement about: (1) Numbering of the elements and their relationship to atomic structure; (2) division of the elements into periods and groups; (3) division of the elements into metals, nonmetals, and metalloids; (4) identification and location of the representative and transition elements. 62. (a) [Rn]7s 2 5f 14 6d 10 7p 5 7 valence electrons, 7s 2 7p 5 (c) F, Cl, Br, I, At (d) halogen family, Period 7 63. (a) The two elements are isotopes. The two elements are adjacent to each other in the same period. 64. Most gases are located in the upper right part of the periodic table (H is an exception). They are nonmetals. Liquids show no pattern. Neither do solids, except the vast majority of solids are metals. 65. excited sulfur atom: electron configuration: 1s 2 2s 2 2p 6 3s 1 3p 5 orbital diagram: - 113 -
66. Electrons are located in seven principal energy levels. The outermost energy level has one electron residing in a 7s orbital. 67. Metals are located on the left side of the periodic table. The elements in Group 1A have only one valence electron and those in Group 2A have only two valence electrons. All metals easily lose their valence electrons to obtain a Noble Gas configuration. Nonmetals are located on the right side of the periodic table where they are only a few electrons short of a noble gas configuration. Nonmetals gain valence electrons to obtain a noble gas configuration. 68. On the periodic table, the period number corresponds to the principal energy level in which the s and p sublevels are filling. The group number of the Main Representative elements corresponds to the number of electrons filling in the principal energy level. Groups 1A and 2A are known as the s-block elements and Groups 3A through 8A are known as the p-block elements. - 114 -