Periodic Law - Interactive Reader.pdf - SECTION 5.2 Electron Configuration and the Periodic Table Mendeleev and the scientists who built upon his work

Periodic Law - Interactive Reader.pdf - SECTION 5.2...

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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. SECTION 5.2 Electron Configuration and the Periodic Table alkali metal alkaline-earth metal transition element main-group element halogen K EY T ERMS READING CHECK 1. How many electrons does a noble gas, other than helium, have in its highest-occupied energy level? The period of an element is determined by its electron configuration. 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 fi lling 1 2 1 s 2 8 2 s 2 p 3 8 3 s 3 p 4 18 4 s 3 d 4 p 5 18 5 s 4 d 5 p 6 32 6 s 4 f 5 d 6 p 7 32 7 s 5 f 6 d 7 p 136 CHAPTER 5 8 8
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115 117 118 3 Li 11 Na 19 K 37 Rb 55 Cs 87 Fr 4 Be 12 Mg 20 Ca 38 Sr 56 Ba 88 Ra 5 B 13 Al 31 Ga 49 In 81 Tl 6 C 14 Si 32 Ge 50 Sn 82 Pb 7 N 15 P 33 As 51 Sb 83 Bi 8 O 16 S 34 Se 52 T e 84 P o 9 F 17 Cl 35 Br 53 I 85 At 21 Sc 39 Y 57 La 89 Ac 22 Ti 40 Zr 72 Hf 104 Rf 23 V 41 Nb 73 T a 105 Db 24 Cr 42 Mo 74 W 106 Sg 25 Mn 43 Tc 75 Re 107 Bh 26 F e 44 Ru 76 Os 108 Hs 27 Co 45 Rh 77 Ir 109 Mt 28 Ni 46 Pd 78 Pt 110 Ds 29 Cu 47 Ag 79 Au 111 Rg 112 Cn 30 Zn 48 Cd 80 Hg Group 1 10 Ne 18 Ar 36 Kr 54 Xe 86 Rn 66 Dy 98 Cf 67 Ho 99 Es 68 Er 100 Fm 69 Tm 101 Md 70 Yb 102 No 58 Ce 90 Th 59 Pr 91 P a 60 Nd 92 U 61 Pm 93 Np 62 Sm 94 Pu 63 Eu 95 Am 64 Gd 96 Cm 65 Tb 97 Bk 71 Lu 103 Lr Group 18 Group 2 Group 3 Group 4 Group 5 Group 6 Group 7 Group 8 Group 9 Group 10 Group 11 Group 12 Group 13 Group 14 Group 15 Group 17 Group 16 s -block elements p -block elements d -block elements f -block elements 1 H 2 He 114 Fl 116 Lv 113 Nh Mc Ts Og In the first period, the 1 s 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 fi fth periods, the d sublevel is filled with 10 electrons, for a total of 18 electrons.
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