Electron Configuration and the Periodic Table

Transcription

1 SECTION 5.2 Electron Configuration and the Periodic Table Mendeleev and the scientists who built upon his work arranged the elements in a periodic table that reflected the similarity of their properties. For example, all of the Group 18 elements, the noble gases, are stable, undergoing few chemical reactions. The reason for this stability has to do with the number of electrons in the highest-occupied energy level. Each noble gas, except for helium, has an octet of electrons in the highest-occupied energy level. This configuration is stable, making removal of electrons difficult. The period of an element is determined by its electron configuration. alkali metal alkaline-earth metal transition element main-group element halogen Key Terms READING CHECK 1. How many electrons does a noble gas, other than helium, have in its highest-occupied energy level? In the chapter Arrangement of Electrons in Atoms, you learned that you can determine the period of an element directly from its configuration. The highest-occupied energy level for an atom of any element determines the element s period. For example, arsenic s electron configuration is [Ar]3 d 10 4 s 2 4 p 3. Therefore, the highest-occupied energy level for arsenic is the n = 4 level. The table below restates the order at which sublevels fill with electrons. The table shows that the number of sublevels filled determines the length of the period. Relationship Between Period Length and Sublevels Being Filled Period number Number of elements in period Sublevels in order of filling 1 2 1s 2 8 2s 2p 3 8 3s 3p s 3d 4p s 4d 5p s 4f 5d 6p s 5f 6d 7p 130 CHAPTER 5

2 1 H Group 1 3 Li 11 Na 19 K Group 2 4 Be 12 Mg 20 Ca 21 Sc 22 Ti 23 V s -block elements p -block elements d -block elements f -block elements G r oup 3 G r oup 4 G r oup 5 G r oup 6 G r oup 7 G r oup 8 G r oup 9 G r oup 10 G r oup 11 G r oup Cr 25 Mn 26 F e 27 Co 28 Ni 29 Cu 30 Zn G r oup 13 G r oup 14 G r oup 15 G r oup 16 G r oup 17 5 B 13 Al 31 Ga 6 C 14 Si 32 Ge 7 N 15 P 33 As 8 O 16 S 34 Se 9 F 17 Cl 35 Br G r oup 18 2 He 10 Ne 18 Ar 36 Kr 37 Rb 38 Sr 39 Y 40 Zr 41 Nb 42 Mo 43 Tc 44 Ru 45 Rh 46 Pd 47 Ag 48 Cd 49 In 50 Sn 51 Sb 52 T e 53 I 54 Xe 55 Cs 56 Ba 57 La 72 Hf 73 T a 74 W 75 Re 76 Os 77 Ir 78 Pt 79 Au 80 Hg 81 Tl 82 Pb 83 Bi 84 P o 85 At 86 Rn 87 Fr 88 Ra 89 Ac 104 Rf 105 Db 106 Sg 107 Bh 108 Hs 109 Mt 110 Ds 111 Rg 112 Cn 58 Ce 59 Pr 60 Nd 61 Pm 62 Sm 63 Eu 64 Gd 65 Tb 66 Dy 67 Ho 68 Er 69 Tm 70 Yb 71 Lu 90 Th 91 P a 92 U 93 Np 94 Pu 95 Am 96 Cm 97 Bk 98 Cf 99 Es 100 Fm 101 Md 102 No 103 Lr In the first period, the 1s orbital is filled with two electrons. In the second and third periods, the s sublevel is filled with two electrons and the p sublevel is filled with six electrons, for a total of eight electrons. In the fourth and fifth periods, the d sublevel is filled with 10 electrons, for a total of 18 electrons. Finally, in the sixth and seventh periods, the f sublevel is filled with an additional 14 electrons, for a total of 32 electrons. The periodic table can be divided into four blocks based on the electron configurations of the elements. By examining the electron configurations of the elements, you can see that the horizontal location of an element in the periodic table is also related to its configuration. For example, in Group 2, the last electron fills the s sublevel. Therefore, the periodic table can be divided into four blocks depending on which sublevel the last electron fills. The periodic table above shows the result of this division. The four blocks are the s block, the p block, the d block, and the f block. READING CHECK 2. The last electron in arsenic occupies a 4p level. What block of the periodic table is arsenic in? The Periodic Law 131

3 LKell Periodic Table of the Elements Period H Hydrogen s 1 Group 1 Group 2 Atomic number 3 4 Symbol Li Lithium Beryllium [He]2s 1 [He]2s 2 11 Na Sodium [Ne]3s 1 19 K Be 12 Mg Magnesium Name Average atomic mass Electron configuration Aluminum [Ne]3s 2 3p 1 [Ne]3s 2 Group 3 Group 4 Group 5 Group 6 Group 7 Group 8 Group 9 20 Ca 21 Sc 22 Ti 23 V Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt [Ar]4s 1 [Ar]4s 2 [Ar]3d 1 4s 2 [Ar]3d 2 4s 2 [Ar]3d 3 4s 2 [Ar]3d 5 4s 1 [Ar]3d 5 4s 2 [Ar]3d 6 4s 2 [Ar]3d 7 4s 2 24 Cr Key: 13 Al 25 Mn 26 Fe 27 Co 5 37 Rb Rubidium [Kr]5s 1 38 Sr Strontium [Kr]5s 2 39 Y Yttrium [Kr]4d 1 5s 2 40 Zr Zirconium [Kr]4d 2 5s 2 41 Nb Niobium [Kr]4d 4 5s 1 42 Mo Molybdenum [Kr]4d 5 5s 1 43 Tc Technetium (98) [Kr]4d 6 5s 1 44 Ru Ruthenium [Kr]4d 7 5s 1 45 Rh Rhodium [Kr]4d 8 5s Cs Cesium [Xe]6s 1 56 Ba Barium [Xe]6s 2 57 La Lanthanum [Xe]5d 1 6s 2 72 Hf Hafnium [Xe]4f 14 5d 2 6s 2 73 Ta Tantalum [Xe]4f 14 5d 3 6s 2 74 W Tungsten [Xe]4f 14 5d 4 6s 2 75 Re Rhenium [Xe]4f 14 5d 5 6s Os Ir Osmium Iridium [Xe]4f 14 5d 6 6s 2 [Xe]4f 14 5d 7 6s Fr Francium (223) [Rn]7s 1 88 Ra Radium (226) [Rn]7s 2 89 Ac Actinium (227) [Rn]6d 1 7s Rf Rutherfordium (261) [Rn]5f 14 6d 2 7s Db Dubnium (262) [Rn]5f 14 6d 3 7s Sg Seaborgium (266) [Rn]5f 14 6d 4 7s Bh Bohrium (264) [Rn]5f 14 6d 5 7s Hs Hassium (277) [Rn]5f 14 6d 6 7s Mt Meitnerium (268) [Rn]5f 14 6d 7 7s 2 * The systematic names and symbols for elements greater than 112 will be used until the approval of trivial names by IUPAC. Elements whose average atomic masses appear bolded and italicized are recognized by the International Union of Pure and Applied Chemistry (IUPAC) to have several stable isotopes. Thus, the average atomic mass for each of these elements is officially expressed as a range of values. A range of values expresses that the average atomic mass of a sample of one of these elements is not a constant in nature but varies depending on the physical, chemical, and nuclear history of the material in which the sample is found. However, the values in this table are appropriate for everyday calculations. A value given in parentheses is not an average atomic mass but is the mass number of that element's most stable or most common isotope. 58 Ce Cerium [Xe]4f 1 5d 1 6s 2 90 Th Thorium [Rn]6d 2 7s 2 59 Pr Praseodymium [Xe]4f 3 6s 2 91 Pa Protactinium [Rn]5f 2 6d 1 7s 2 60 Nd Neodymium [Xe]4f 4 6s 2 92 U Uranium [Rn]5f 3 6d 1 7s 2 61 Pm Promethium (145) [Xe]4f 5 6s 2 93 Np Neptunium (237) [Rn]5f 4 6d 1 7s 2 62 Sm Samarium [Xe]4f 6 6s 2 94 Pu Plutonium (244) [Rn]5f 6 7s CHAPTER 5

4 Hydrogen Semiconductors (also known as metalloids) Metals Alkali metals Alkaline-earth metals Transition metals Other metals Nonmetals Halogens Noble gases Other nonmetals Group 10 Group 11 Group 12 Group 18 Helium s Group 13 Group 14 Group 15 Group 16 Group B C N O F Ne Boron Carbon Nitrogen Oxygen Fluorine Neon [He]2s 2 2p 1 [He]2s 2 2p 2 [He]2s 2 2p 3 [He]2s 2 2p 4 [He]2s 2 2p 5 [He]2s 2 2p Al Si P S Cl Ar Aluminum Silicon Phosphorus Sulfur Chlorine Argon [Ne]3s 2 3p 1 [Ne]3s 2 3p 2 [Ne]3s 2 3p 3 [Ne]3s 2 3p 4 [Ne]3s 2 3p 5 [Ne]3s 2 3p 6 2 He Ni Cu Zn Ga Ge As Se Br Kr Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton [Ar]3d 8 4s 2 [Ar]3d 10 4s 1 [Ar]3d 10 4s 2 [Ar]3d 10 4s 2 4p 1 [Ar]3d 10 4s 2 4p 2 [Ar]3d 10 4s 2 4p 3 [Ar]3d 10 4s 2 4p 4 [Ar]3d 10 4s 2 4p 5 [Ar]3d 10 4s 2 4p Pd Ag Cd In Sn Sb Te I Xe Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon [Kr]4d 10 [Kr]4d 10 5s 1 [Kr]4d 10 5s 2 [Kr]4d 10 5s 2 5p 1 [Kr]4d 10 5s 2 5p 2 [Kr]4d 10 5s 2 5p 3 [Kr]4d 10 5s 2 5p 4 [Kr]4d 10 5s 2 5p 5 [Kr]4d 10 5s 2 5p 6 78 Pt Platinum [Xe]4f 14 5d 9 6s Au Hg Tl Pb Bi Po At Rn Gold Mercury Thallium Lead Bismuth Polonium Astatine Radon (209) (210) (222) [Xe]4f 14 5d 10 6s 1 [Xe]4f 14 5d 10 6s 2 [Xe]4f 14 5d 10 6s 2 6p 1 [Xe]4f 14 5d 10 6s 2 6p 2 [Xe]4f 14 5d 10 6s 2 6p 3 [Xe]4f 14 5d 10 6s 2 6p 4 [Xe]4f 14 5d 10 6s 2 6p 5 [Xe]4f 14 5d 10 6s 2 6p Ds Rg Cn Uut * Uuq * Uup * Darmstadtium Roentgenium Copernicium Ununtrium Ununquadium Ununpentium (271) (272) (285) (284) (289) (288) [Rn]5f 14 6d 9 7s 1 [Rn]5f 14 6d 10 7s 1 [Rn]5f 14 6d 10 7s 2 [Rn]5f 14 6d 10 7s 2 7p 1 [Rn]5f 14 6d 10 7s 2 7p 2 [Rn]5f 14 6d 10 7s 2 7p 3 The discoveries of elements with atomic numbers have been reported but not fully confirmed. 116 Uuh * Ununhexium (292) 117 Uus * Ununseptium (294) 118 Uuo * Ununoctium (294) [Rn]5f 14 6d 10 7s 2 7p [Rn]5f 14 6d 10 7s 2 7p [Rn]5f 14 6d 10 7s 2 7p Eu Europium [Xe]4f 7 6s 2 64 Gd Gadolinium [Xe]4f 7 5d 1 6s 2 65 Tb Terbium [Xe]4f 9 6s 2 66 Dy Dysprosium [Xe]4f 10 6s 2 67 Ho Holmium [Xe]4f 11 6s 2 68 Er Erbium [Xe]4f 12 6s 2 69 Tm Thulium [Xe]4f 13 6s 2 70 Yb Ytterbium [Xe]4f 14 6s 2 71 Lu Lutetium [Xe]4f 14 5d 1 6s 2 95 Am Americium (243) [Rn]5f 7 7s 2 96 Cm Curium (247) [Rn]5f 7 6d 1 7s 2 97 Bk Berkelium (247) [Rn]5f 9 7s 2 98 Cf Californium (251) [Rn]5f 10 7s 2 99 Es Einsteinium (252) [Rn]5f 11 7s Fm Fermium (257) [Rn]5f 12 7s Md Mendelevium (258) [Rn]5f 13 7s No Nobelium (259) [Rn]5f 14 7s Lr Lawrencium (262) [Rn]5f 14 6d 1 7s 2 The Periodic Law 133

5 The s-block Elements: Groups 1 and 2 The elements in the s-block are chemically reactive metals. The Group 1 metals are more reactive than the Group 2 metals. As you will learn in Section 3, Group 1 metals are reactive because the single electron in their highest-occupied energy level is easily lost. The elements in Group 1 (lithium, sodium, potassium, rubidium, cesium, and francium) are known as the alkali metals. In their pure state, all of the alkali metals have a silvery appearance and are soft enough to cut with a knife. As you move down the column in the periodic table, the pure forms of these elements melt at lower and lower temperatures. Some groups in the periodic table are also represented by their own configuration. This notation reflects the fact that each element in the group has the same configuration in its highest-occupied energy level. For example, Group 1 has a group configuration of n s 1, and Group 2 has a group configuration of n s 2. TIP READING CHECK 3. Which is more reactive, potassium or calcium? (a) Potassium reacts so strongly with water that (b) it must be stored in kerosene to prevent it from contacting moisture in the air. (a) (b) However, because the alkali metals are so reactive, they are not found in nature as free elements. Each element reacts with water to form hydrogen gas and a solution known as an alkali. They also react with most nonmetals. To prevent pure forms of these elements from reacting, they are stored in jars and completely covered with kerosene. The elements in Group 2 (beryllium, magnesium, calcium, strontium, barium, and radium) are called the alkaline-earth metals. Atoms of alkaline-earth metals have a pair of electrons in their outermost s sublevel. The Group 2 metals are harder and denser than the alkali metals. They also have higher melting points. Although they are less reactive than the alkali metals, the alkaline-earth metals are also too reactive to be found in nature as free elements. Beryllium is found in the mineral compound beryl. Beryl crystals include the blue-green aquamarine and the dark green emerald. 134 CHAPTER 5

6 SAMPLE PROBLEM a. Without looking at the periodic table, identify the group, period, and block in which the element that has the electron configuration [Xe]6 s 2 is located. b. Without looking at the periodic table, write the electron configuration for the Group 1 element in the third period. SOLUTION 1 ANALYZE Determine what information is given and unknown. Given: a. [Xe]6 s 2 b. Group 1, third period Unknown: a. group, period, block b. electron configuration 2 PLAN Determine the information necessary to answer the questions. The location of an element in the periodic table is directly related to its electron configuration. 3 SOLVE Determine the unknowns from the given information. a. The element is in the sixth period because its highestoccupied energy level is n = 6. Because its configuration is of the form n s 2, it is in Group 2, which is in the s block. b. The group configuration of Group 1 elements is n s 2. Since the element is in the third period, n = 3, the electron configuration is 1 s 2 2 s 2 2 p 6 3 s 1, or [Ne]3 s 1. 4 CHECK YOUR WORK Determine if the answers make sense. The configuration of each element matches the group and period describing the element s location in the periodic table. PRACTICE Answer without looking at the periodic table. A. Identify the following for the element with the electron configuration [Kr]5 s 1. Group number Period number Block designation B. Write the noble-gas configuration for the Group 2 element in the fourth period. The Periodic Law 135

7 Hydrogen and Helium Hydrogen has the electron configuration 1 s 1, but does not share the same properties as the Group 1 elements. It is a unique element, whose properties do not closely resemble those of any group. It is usually placed above the Group 1 elements with a gap between it and lithium. Helium has the same n s 2 configuration as the Group 2 elements. However, it has the stability of a noble gas because its outermost energy level is filled. It is placed in Group 18, instead of with the reactive, unstable Group 2 elements. The d-block Elements: Groups 3 12 The d-block elements are metals with typical metallic properties and are often referred to as transition elements or transition metals. They are good conductors of electricity and have a high luster. They are usually less reactive than the alkali metals and alkaline-earth metals. Some transition elements, such as gold, palladium, and platinum, are so unreactive that they exist in nature mostly as free elements. The last electron placed in an atom of a d-block element is in a d orbital. The d block spans ten groups on the periodic table. The group configuration of Group 3 elements is (n 1) d 1 n s 2. For example, scandium has the configuration [Ar]3 d 1 4 s 2, as shown below. The group configuration of Group 12 elements is (n 1) d 10 n s 2. One example is mercury, with the configuration [Xe]4 f 14 5 d 10 6 s 2. Groups 4 11 do not have regular configurations, but the sum of the electrons in the highest s and d sublevels is always equal to the group number. The transition element copper is found in nature as part of copper ore and can be obtained from surface mines. (a) Energy 1s 2s 2p 3s 3p 4s 3d (b) The pure forms of (a) tungsten and (b) vanadium are shown. The electron configuration of the fourth-period, Group 3 element Scandium, Sc. READING CHECK 4. Name at least three properties of a transition element. 136 CHAPTER 5

8 SAMPLE PROBLEM An element has the electron configuration [Kr]4 d 5 5 s 1. Without looking at the periodic table, identify the period, block, and group in which this element is located. Then, consult the periodic table to identify this element. SOLUTION 1 ANALYZE Determine what information is given and unknown. Given: the electron configuration [Kr]4 d 5 5 s 1 Unknown: period, block, group, other elements in group 2 PLAN Determine the information needed to answer the questions. The location of an element in the periodic table is directly related to its electron configuration. 3 SOLVE Determine the unknowns from the given information. The element is in the fifth period because its highest-occupied energy level is n = 5. There are five electrons in the d sublevel, which means that the sublevel is not completely filled. It also means that the element is in the d block. The sum of the electrons in the highest s and d levels is six, so the element is in Group 6. The fifth-period element in Group 6 of the periodic table is molybdenum. 4 CHECK YOUR WORK PRACTICE Determine if the answers make sense. The configuration of molybdenum matches the group and period describing its location in the periodic table. Answer without looking at the periodic table. C. Identify the following for the element with the electron configuration [Ar]3 d 8 4 s 2. Period number Block designation Group number D. Write the outer electron configuration for the Group 12 element in the fifth period. The Periodic Law 137

9 Relationships Among Group Numbers, Blocks, and Electron Configurations Group number Group configuration Block Comments 1, 2 n s 1, 2 s One or two electrons in ns sublevel 3 12 (n - 1) d 1 10 n s 0 2 d Sum of electrons in ns and (n - 1)d levels equals group number n s 2 n 1 6 p Number of electrons in np sublevel group number minus 12 The p-block Elements: Groups The p-block elements consist of all the elements in Groups except helium. In the atoms of these elements, the final electron fills the p sublevel. Because electrons are added to the p sublevel only after the s sublevel is filled, each element in the p block also has two electrons in every s sublevel. The p-block elements, along with the s-group elements are called the main-group elements. The group configurations for the p block, as well as the s and d blocks, are summarized in the table at the top of the page. You can conclude from the table, for example, that the group configuration for Group 15 is n s 2 n p 3. For atoms of p-block elements, the total number of electrons in the highest-occupied energy level is equal to the group number minus 10. For example, bromine is in Group 17. It has = 7 electrons in its highest energy level. The properties of the elements in the p block vary greatly. The right side of the p block contains all of the nonmetals except hydrogen and helium. All six of the metalloids (boron, silicon, germanium, arsenic, antimony, and tellurium) are also in the p block. The bottom left of the p block contains eight metals. 5 B 13 Al 31 Ga 49 In 81 Tl Metals Metalloids Nonmetals Group 13 Group 14 Group 15 Group 16 Group 17 6 C 14 Si 32 Ge 50 Sn 82 Pb 7 N 15 P 33 As 51 Sb 83 Bi! Remember 8 O 16 S 34 Se 52 Te 84 Po 9 F 17 Cl 35 Br 53 I 85 At Group 18 2 He 10 Ne 18 Ar 36 Kr 54 Xe 86 Rn Groups of the periodic table, which includes the p block and helium. A nonmetal is a poor conductor of electricity and heat. A metalloid, or semiconductor, has some properties of metals and some properties of nonmetals. READING CHECK 5. What is the group configuration of the elements in Group 17? 138 CHAPTER 5

10 (a) (b) (c) (d) The elements in Group 17 (fluorine, chlorine, bromine, iodine, and astatine) are called the halogens. The halogens are the most reactive nonmetals. They react vigorously with most metals to form salts. At room temperature, fluorine and chlorine are gases, bromine is a reddish liquid, and iodine is a purplish solid. Astatine is an artificial element. The halogens in Group 17 include (a) fluorine, (b) chlorine, (c) bromine, and (d) iodine. Halogens are reactive because they are one electron short of a stable octet. TIP The metalloids of the p block are mostly brittle solids. They have an electrical conductivity that is in between that of metals, which are good conductors, and nonmetals, which are poor conductors. The metals of the p block are usually harder and denser than the alkali metals and alkaline-earth metals of the s block, but softer and less dense than the metals of the d block. With the exception of bismuth, these metals are reactive enough to be found in nature only in compounds. However, once a pure metal is obtained, the element is stable in the presence of air. The f-block Elements: Lanthanides and Actinides The f-block elements are wedged between Group 3 and Group 4 of the periodic table. There are seven orbitals to be filled with two electrons each on the f sublevel. Therefore, the f block is 2 7 = 14 elements wide. The lanthanides are the 14 elements in the sixth period. They are shiny metals similar in reactivity to the alkalineearth metals. The actinides are the 14 elements in the seventh period. All of the actinides are radioactive. Only the first four actinides thorium, protactinium, uranium, and neptunium have been found on Earth. The others were made in the laboratory. READING CHECK 6. Which blocks of the periodic table contain elements that are considered metals? The Periodic Law 139

11 SAMPLE PROBLEM Without looking at the periodic table, write the outer electron configuration for the Group 14 element in the second period. Then, name the element and identify it as a metal, nonmetal, or metalloid. SOLUTION 1 ANALYZE Determine what information is given and unknown. Given: a second period element in Group 14 Unknown: outer electron configuration, type of element 2 PLAN Determine the information necessary to answer the questions. The electron configuration of an element in the periodic table is directly related to its location. 3 SOLVE Determine the unknowns from the given information. 4 CHECK YOUR WORK Elements in Group 14 are in the p block. The total number of electrons in the highest occupied s and p sublevels for a Group 14 element is = 4. Two electrons fill the s sublevel first, so the other two electrons must be in the p sublevel. The outer configuration for a Group 14 element in the second period, n = 2, is 2 s 2 2 p 2. The second period element in Group 14 is carbon, C. Carbon is a nonmetal. Determine if the answers make sense. The configuration of carbon matches the group and period describing its location in the periodic table. PRACTICE Answer without looking at the periodic table. E. Write the outer electron configuration for the Group 17 element in the third period. F. Identify the following for the element with the electron configuration [Ar]3 d 10 4 s 2 4 p 3. Period number Block designation Group number 140 CHAPTER 5

12 SAMPLE PROBLEM Use the given electron configuration to determine the period, group, and block for these four elements. Then use the periodic table to name each element, identify it as a metal, nonmetal, or metalloid, and describe its relative reactivity. SOLVE Electron configuration Complete before looking at the periodic table Complete while looking at the periodic table Period Block Group Name Type Reactivity a. [Xe]4 f 14 5 d 9 6 s 1 6 d 10 platinum metal low b. [Ne]3 s 2 3 p 5 3 p 17 chlorine nonmetal high c. [Ne]3 s 2 3 p 6 3 p 18 argon nonmetal low d. [Xe]4 f 6 6 s 2 6 f N/A samarium metal high a. The 5d sublevel is not filled, so the element is in the d block. The group number is = 10. The element is platinum, which is a transition metal and has low reactivity. b. The 3p sublevel is not filled, so the element is in the p block. The group number is = 17. The element is chlorine, a reactive nonmetal. c. This element has a noble-gas configuration, so it is in Group 18. The element is argon, a nonreactive nonmetal. d. The 4f sublevel is not filled, so the element is in the f block. This is a sixth-period element, so it a lanthanide, a reactive metal. The name of the element is samarium. PRACTICE Complete the table below. Fill in the first three columns without consulting the periodic table. Electron configuration Complete before looking at the periodic table Complete while looking at the periodic table Period Block Group Name Type Reactivity G. [He]2 s 2 2 p 5 H. [Ar]3 d 10 4 s 1 The Periodic Law 141

13 SECTION 5.2 REVIEW VOCABULARY 1. What name is given to each of the following groups of elements in the periodic table? a. Group 1 d. Group 17 b. Group 2 e. Group 18 c. Group 3 12 REVIEW 2. Into what four blocks can the periodic table be divided to illustrate the relationship between the elements electron configurations and their placement in the periodic table? 3. What are the relationships between group configuration and group number for elements in the s, p, and d blocks? 4. Without looking at the periodic table, write the outer electron configuration for the Group 15 element in the fourth period. 5. Without looking at the periodic table, identify the period, block, and group of the element that has the electron configuration [Ar]3 d 7 4 s 2. Period number Block designation Group number Critical Thinking 6. APPLYING MODELS Period 7 contains elements in the s, p, d, and f blocks. Suppose there were a Period 8 and it contained elements in the g block, where g had the angular momentum quantum number of 4. If a hypothetical element in Period 8 had an atomic number of 120, into what group in the periodic table would the element fit, and what properties might it have (assuming it does not radioactively decay)? 142 CHAPTER 5