SECTION 5.2 Electron Configuration and the Periodic Table

Electron Configuration and the Periodic Table

SECTION 5.2

Teacher Notes and AnswersSECTION 2 ElECTrON CONfIguraTION aNd ThE PErIOdIC TablE 1. 8 2. the p block 3. potassium 4. Properties of transition metals include electrical

conductivity, high luster, and less reactivity than alkali metals and alkaline-earth metals

5. n s 2 n p 5 6. All four blocks, the s block, the p block, the d

block, and the f block, contain metals.

Practice

a. 1; 5; s block b. [Ar]4 s 2 C. 4; d block; 10 d. 4 d 10 5 s 2 E. 3 s 2 3 p 5 f. 4; p block; 15 g. 2; p block; 17; fluorine; nonmetal; high h. 4; d block; 11; copper; metal; low

Review

1a. alkali metals

1b. alkaline-earth metals 1c. transition metals 1d. halogens 1e. noble gases 2. the s block, the p block, the d block, and the f

block 3. For s-block elements, the number above the s

is the same as the group number. For p-block elements, the sum of the two numbers above the s and the p is equal to the group number minus 10. For d-block elements, the sum of the numbers above the s and the d is equal to the group number.

4. 3 d 10 4 s 2 4 p 3 5. 4; d block; 9 6. An element with the atomic number 120 would

be in Group 2 and would have properties similar to the properties of other alkaline-earth metals. For example, the element would be metallic, have a high melting point, and be less reactive than alkali metals.

1The Periodic Law

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 metalalkaline-earth metaltransition elementmain-group elementhalogen

Key Terms

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 filling

1 2 1s

2 8 2s 2p

3 8 3s 3p

4 18 4s 3d 4p

5 18 5s 4d 5p

6 32 6s 4f 5d 6p

7 32 7s 5f 6d 7p

2 chaPTer 5

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

G r oup 18

Group 2

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 12

G r oup 13 G r oup 14 G r oup 15 G r oup 17 G r oup 16

s -block elements

p -block elements

d -block elements

f -block elements

1

H 2

He

HS_CNLERD704821_1Afinal4-12 -11LKell

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.

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 table can be divided into four blocks based on the electron configurations of the elements.

3The Periodic Law

(292)UnunhexiumUuh*

116

(294)UnunseptiumUus*

117

(294)UnunoctiumUuo*

118

1

2

3

4

5

6

7

Perio

d

* The discoveries of elements with atomic numbers 113–118 have been reported but not fully confirmed.The systematic names and symbolsfor elements greater than 112 willbe used until the approval of trivialnames by IUPAC.

Group 3 Group 4 Group 5 Group 6 Group 7 Group 8 Group 9

Group 1 Group 2 Group 14 Group 15 Group 16 Group 17

Group 18

Group 10 Group 11 Group 12

Group 13

[He]2s1

[Ne]3s1

[Ar]4s1

[He]2s2

[Ne]3s2

[Ar]4s2 [Ar]3d 14s2

1s1

[Ar]3d 24s2 [Ar]3d 34s2 [Ar]3d 54s1 [Ar]3d 54s2 [Ar]3d 64s2 [Ar]3d 74s2

[Kr]5s1

[Xe]6s1

[Rn]7s1

[Kr]5s2

[Xe]6s2

[Rn]7s2

[Kr]4d 15s2

[Xe]5d 16s2

[Rn]6d 17s2

[Kr]4d 25s2

[Xe]4f145d 26s2

[Rn]5f 146d 27s2

[Kr]4d 45s1

[Xe]4f 145d 36s2

[Rn]5f 146d 37s2

[Kr]4d 55s1

[Xe]4f 145d 46s2

[Rn]5f 146d 47s2

[Kr]4d 65s1

[Xe]4f 145d 56s2

[Rn]5f 146d 57s2

[Kr]4d 75s1

[Xe]4f 145d 66s2

[Rn]5f 146d 67s2

[Kr]4d 85s1

[Xe]4f 145d 76s2

[Rn]5f 146d 77s2

[Xe]4 f15d 16s2

[Rn]6d 27s2

[Xe]4 f 36s2

[Rn]5f 26d 17s2

[Xe]4 f 46s2

[Rn]5f 36d 17s2

[Xe]4f 56s2

[Rn]5f 46d 17s2

[Xe]4f 66s2

[Rn]5f 67s2

[Xe]4f 145d16s2[Xe]4f 146s2[Xe]4f 136s2[Xe]4f 126s2[Xe]4f 116s2[Xe]4f 106s2

[Rn]5f 146d17s2[Rn]5f 147s2[Rn]5f 137s2[Rn]5f 127s2[Rn]5f 117s2[Rn]5f 107s2

[Xe]4f 145d106s26p6

[Kr]4d 105s25p6

[Ar]3d 104s24p6

[Ne]3s 23p6

1s 2

[He]2s 22p5[He]2s 22p4[He]2s 22p3[He]2s 22p2[He]2s 22p1

[Ne]3s 23p5[Ne]3s 23p4[Ne]3s 23p3[Ne]3s 23p2[Ne]3s 23p1

[Ar]3d 104s24p5[Ar]3d 104s24p4[Ar]3d 104s24p3[Ar]3d 104s24p2[Ar]3d 104s24p1

[Kr]4d 105s25p5[Kr]4d 105s25p4[Kr]4d 105s25p3[Kr]4d 105s25p2[Kr]4d 105s25p1

[Xe]4f 145d106s26p5[Xe]4f 145d106s26p4[Xe]4f 145d106s26p3[Xe]4f 145d106s26p2[Xe]4f 145d106s26p1

[He]2s 22p6

[Rn]5f 146d 107s27p2 [Rn]5f 146d 107s27p3[Rn]5f 146d 107s27p1

[Xe]4f 96s2[Xe]4f 75d16s2[Xe]4f 76s2

[Rn]5f 97s2[Rn]5f 76d17s2[Rn]5f 77s2

[Ar]3d 104s2[Ar]3d 104s1[Ar]3d 84s2

[Kr]4d 105s2[Kr]4d 105s1[Kr]4d 10

[Xe]4f 145d106s2[Xe]4f 145d96s1

[Rn]5f 146d 97s1 [Rn]5f 146d 107s2[Rn]5f 146d 107s1

[Xe]4f 145d106s1

Electron configuration

[Rn]5f 146d 107s27p4

[Rn]5f 146d 107s27p5

[Rn]5f 146d 107s27p6

6.94

22.989 769 28

39.0983

85.4678

132.905 4519

(223)

140.116

232.038 06

140.907 65

231.035 88

144.242

238.028 91

(145)

(237)

150.36

(244)

9.012 182

24.3050

40.078

87.62

137.327

(226)

44.955 912

88.905 85

138.905 47

(227)

47.867

91.224

178.49

(261)

50.9415

92.906 38

180.947 88

(262)

51.9961

95.94

183.84

(266)

54.938 045

(98)

186.207

(264)

55.845

101.07

190.23

(277)

58.933 195

102.905 50

192.217

(268)

1.008

151.964

(243)

157.25

(247)

158.925 35

(247)

162.500

(251)

164.930 32

(252)

167.259

(257)

168.934 21

(258)

173.04

(259)

174.967

(262)

58.6934 63.546 65.409 69.723 72.63 74.921 60 78.96 79.904 83.798

26.981 5386

26.981 5386

28.085 30.973 762 32.06 35.45 39.948

12.01 1 14.007 15.999 18.998 4032 20.1797

4.002 602

106.42 107.8682 112.411 114.818 118.710 121.760 127.60 126.904 47 131.293

195.084

(271) (272) (284) (289) (288)

196.966 569 200.59 204.38 207.2 208.980 40 (209) (210) (222)

10.81Lithium

Sodium

Potassium

Rubidium

Cesium

Francium

Cerium

Thorium

Praseodymium

Protactinium

Neodymium

Uranium

Promethium

Neptunium

Samarium

Plutonium

Beryllium

Magnesium

Calcium

Strontium

Barium

Radium

Scandium

Yttrium

Lanthanum

Actinium

Titanium

Zirconium

Hafnium

Rutherfordium

Vanadium

Niobium

Tantalum

Dubnium

Chromium

Molybdenum

Tungsten

Seaborgium

Manganese

Technetium

Rhenium

Bohrium

Iron

Ruthenium

Osmium

Hassium

Cobalt

Rhodium

Iridium

Meitnerium

Hydrogen

Europium

Americium

Gadolinium

Curium

Terbium

Berkelium

Dysprosium

Californium

Holmium

Einsteinium

Erbium

Fermium

Thulium

Mendelevium

Ytterbium

Nobelium

Lutetium

Lawrencium

Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton

Aluminum

Aluminum

Silicon Phosphorus Sulfur Chlorine Argon

Carbon Nitrogen Oxygen Fluorine Neon

Helium

Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon

Platinum

Darmstadtium Roentgenium Ununtrium Ununquadium Ununpentium

Gold Mercury Thallium Lead Bismuth Polonium Astatine Radon

Boron

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.

112

CnCopernicium

(285)

Eu

Am

Gd

Cm

Tb

Bk

Dy

Cf

Ni Cu Zn Ga Ge As Se Br Kr

Al

Al

Si P S Cl Ar

C N O F Ne

He

Pd Ag Cd In Sn Sb Te I Xe

Pt

Ds Rg Uut* Uuq* Uup*

Au Hg Tl Pb Bi Po At Rn

Ho

Es

Er

Fm

Tm

Md

Yb

No

Lu

Lr

BLi

V

Na

K

Rb

Cs

Fr

Be

Mg

Ca

Sr

Ba

Ra

Sc

Y

La

Ac

Ti

Zr

Hf

Rf

Nb

Ta

Db

Cr

Mo

W

Sg

Mn

Tc

Re

Bh

IrOs

Ce

Th

Pr

Pa

Nd

U

Pm

Np

Sm

Pu

Fe

Ru

Hs

Co

Rh

Mt

H

3

11

19

37

55

87

4

12

20

38

56

88

21

39

57

89

22

40

72

104

23

41

73

105

24

42

74

106

25

43

75

107

26

44

76 77

108

27

45

109

1

58

90

59

91

60

92

61

93

62

94

63

95

64

96

65

97

66

98

67

99

68

100

69

101

70

102

71

103

28 29 30 31 32 33 34 35 36

13

13

14 15 16 17 18

6 7 8 9 10

2

46 47 48 49 50 51 52 53 54

78

110 111 113 114 115

79 80 81 82 83 84 85 86

5

[Ne]3s 23p1

HydrogenSemiconductors(also known as metalloids)

MetalsAlkali metalsAlkaline-earth metalsTransition metalsOther metals

NonmetalsHalogensNoble gasesOther nonmetals

Key:

Atomic number

Symbol

Name

Average atomic mass

Periodic Table of the Elements


4 chaPTer 5

(292)UnunhexiumUuh*

116

(294)UnunseptiumUus*

117

(294)UnunoctiumUuo*

118

1

2

3

4

5

6

7

Perio

d

* The discoveries of elements with atomic numbers 113–118 have been reported but not fully confirmed.The systematic names and symbolsfor elements greater than 112 willbe used until the approval of trivialnames by IUPAC.

Group 3 Group 4 Group 5 Group 6 Group 7 Group 8 Group 9

Group 1 Group 2 Group 14 Group 15 Group 16 Group 17

Group 18

Group 10 Group 11 Group 12

Group 13

[He]2s1

[Ne]3s1

[Ar]4s1

[He]2s2

[Ne]3s2

[Ar]4s2 [Ar]3d 14s2

1s1

[Ar]3d 24s2 [Ar]3d 34s2 [Ar]3d 54s1 [Ar]3d 54s2 [Ar]3d 64s2 [Ar]3d 74s2

[Kr]5s1

[Xe]6s1

[Rn]7s1

[Kr]5s2

[Xe]6s2

[Rn]7s2

[Kr]4d 15s2

[Xe]5d 16s2

[Rn]6d 17s2

[Kr]4d 25s2

[Xe]4f145d 26s2

[Rn]5f 146d 27s2

[Kr]4d 45s1

[Xe]4f 145d 36s2

[Rn]5f 146d 37s2

[Kr]4d 55s1

[Xe]4f 145d 46s2

[Rn]5f 146d 47s2

[Kr]4d 65s1

[Xe]4f 145d 56s2

[Rn]5f 146d 57s2

[Kr]4d 75s1

[Xe]4f 145d 66s2

[Rn]5f 146d 67s2

[Kr]4d 85s1

[Xe]4f 145d 76s2

[Rn]5f 146d 77s2

[Xe]4 f15d 16s2

[Rn]6d 27s2

[Xe]4 f 36s2

[Rn]5f 26d 17s2

[Xe]4 f 46s2

[Rn]5f 36d 17s2

[Xe]4f 56s2

[Rn]5f 46d 17s2

[Xe]4f 66s2

[Rn]5f 67s2

[Xe]4f 145d16s2[Xe]4f 146s2[Xe]4f 136s2[Xe]4f 126s2[Xe]4f 116s2[Xe]4f 106s2

[Rn]5f 146d17s2[Rn]5f 147s2[Rn]5f 137s2[Rn]5f 127s2[Rn]5f 117s2[Rn]5f 107s2

[Xe]4f 145d106s26p6

[Kr]4d 105s25p6

[Ar]3d 104s24p6

[Ne]3s 23p6

1s 2

[He]2s 22p5[He]2s 22p4[He]2s 22p3[He]2s 22p2[He]2s 22p1

[Ne]3s 23p5[Ne]3s 23p4[Ne]3s 23p3[Ne]3s 23p2[Ne]3s 23p1

[Ar]3d 104s24p5[Ar]3d 104s24p4[Ar]3d 104s24p3[Ar]3d 104s24p2[Ar]3d 104s24p1

[Kr]4d 105s25p5[Kr]4d 105s25p4[Kr]4d 105s25p3[Kr]4d 105s25p2[Kr]4d 105s25p1

[Xe]4f 145d106s26p5[Xe]4f 145d106s26p4[Xe]4f 145d106s26p3[Xe]4f 145d106s26p2[Xe]4f 145d106s26p1

[He]2s 22p6

[Rn]5f 146d 107s27p2 [Rn]5f 146d 107s27p3[Rn]5f 146d 107s27p1

[Xe]4f 96s2[Xe]4f 75d16s2[Xe]4f 76s2

[Rn]5f 97s2[Rn]5f 76d17s2[Rn]5f 77s2

[Ar]3d 104s2[Ar]3d 104s1[Ar]3d 84s2

[Kr]4d 105s2[Kr]4d 105s1[Kr]4d 10

[Xe]4f 145d106s2[Xe]4f 145d96s1

[Rn]5f 146d 97s1 [Rn]5f 146d 107s2[Rn]5f 146d 107s1

[Xe]4f 145d106s1


[Rn]5f 146d 107s27p4

[Rn]5f 146d 107s27p5

[Rn]5f 146d 107s27p6

6.94

22.989 769 28

39.0983

85.4678

132.905 4519

(223)

140.116

232.038 06

140.907 65

231.035 88

144.242

238.028 91

(145)

(237)

150.36

(244)

9.012 182

24.3050

40.078

87.62

137.327

(226)

44.955 912

88.905 85

138.905 47

(227)

47.867

91.224

178.49

(261)

50.9415

92.906 38

180.947 88

(262)

51.9961

95.94

183.84

(266)

54.938 045

(98)

186.207

(264)

55.845

101.07

190.23

(277)

58.933 195

102.905 50

192.217

(268)

1.008

151.964

(243)

157.25

(247)

158.925 35

(247)

162.500

(251)

164.930 32

(252)

167.259

(257)

168.934 21

(258)

173.04

(259)

174.967

(262)

58.6934 63.546 65.409 69.723 72.63 74.921 60 78.96 79.904 83.798

26.981 5386

26.981 5386

28.085 30.973 762 32.06 35.45 39.948

12.01 1 14.007 15.999 18.998 4032 20.1797

4.002 602

106.42 107.8682 112.411 114.818 118.710 121.760 127.60 126.904 47 131.293

195.084

(271) (272) (284) (289) (288)

196.966 569 200.59 204.38 207.2 208.980 40 (209) (210) (222)

10.81Lithium

Sodium

Potassium

Rubidium

Cesium

Francium

Cerium

Thorium

Praseodymium

Protactinium

Neodymium

Uranium

Promethium

Neptunium

Samarium

Plutonium

Beryllium

Magnesium

Calcium

Strontium

Barium

Radium

Scandium

Yttrium

Lanthanum

Actinium

Titanium

Zirconium

Hafnium

Rutherfordium

Vanadium

Niobium

Tantalum

Dubnium

Chromium

Molybdenum

Tungsten

Seaborgium

Manganese

Technetium

Rhenium

Bohrium

Iron

Ruthenium

Osmium

Hassium

Cobalt

Rhodium

Iridium

Meitnerium

Hydrogen

Europium

Americium

Gadolinium

Curium

Terbium

Berkelium

Dysprosium

Californium

Holmium

Einsteinium

Erbium

Fermium

Thulium

Mendelevium

Ytterbium

Nobelium

Lutetium

Lawrencium

Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton

Aluminum

Aluminum

Silicon Phosphorus Sulfur Chlorine Argon

Carbon Nitrogen Oxygen Fluorine Neon

Helium

Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon

Platinum

Darmstadtium Roentgenium Ununtrium Ununquadium Ununpentium

Gold Mercury Thallium Lead Bismuth Polonium Astatine Radon

Boron

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.

112

CnCopernicium

(285)

Eu

Am

Gd

Cm

Tb

Bk

Dy

Cf

Ni Cu Zn Ga Ge As Se Br Kr

Al

Al

Si P S Cl Ar

C N O F Ne

He

Pd Ag Cd In Sn Sb Te I Xe

Pt

Ds Rg Uut* Uuq* Uup*

Au Hg Tl Pb Bi Po At Rn

Ho

Es

Er

Fm

Tm

Md

Yb

No

Lu

Lr

BLi

V

Na

K

Rb

Cs

Fr

Be

Mg

Ca

Sr

Ba

Ra

Sc

Y

La

Ac

Ti

Zr

Hf

Rf

Nb

Ta

Db

Cr

Mo

W

Sg

Mn

Tc

Re

Bh

IrOs

Ce

Th

Pr

Pa

Nd

U

Pm

Np

Sm

Pu

Fe

Ru

Hs

Co

Rh

Mt

H

3

11

19

37

55

87

4

12

20

38

56

88

21

39

57

89

22

40

72

104

23

41

73

105

24

42

74

106

25

43

75

107

26

44

76 77

108

27

45

109

1

58

90

59

91

60

92

61

93

62

94

63

95

64

96

65

97

66

98

67

99

68

100

69

101

70

102

71

103

28 29 30 31 32 33 34 35 36

13

13

14 15 16 17 18

6 7 8 9 10

2

46 47 48 49 50 51 52 53 54

78

110 111 113 114 115

79 80 81 82 83 84 85 86

5

[Ne]3s 23p1

HydrogenSemiconductors(also known as metalloids)

MetalsAlkali metalsAlkaline-earth metalsTransition metalsOther metals

NonmetalsHalogensNoble gasesOther nonmetals

Key:

Atomic number

Symbol

Name

Average atomic mass

Periodic Table of the Elements


5The Periodic Law

(a) (b)

The s-Block Elements: Groups 1 and 2The 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.

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.

(a) Potassium reacts so strongly with water that (b) it must be stored in kerosene to prevent it from contacting moisture in the air.

Beryllium is found in the mineral compound beryl. Beryl crystals include the blue-green aquamarine and the dark green emerald.

READING CHECK

3. Which is more reactive, potassium or calcium?

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

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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 highest- occupied 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 .

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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.

7The Periodic Law

Ener

gy

1s2s 2p

3s 3p

4s 3d

(a)

(b)

Hydrogen and HeliumHydrogen 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 3–12The 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 electron configuration of the fourth-period, Group 3 element Scandium, Sc.

The transition element copper is found in nature as part of copper ore and can be obtained from surface mines.

The pure forms of (a) tungsten and (b) vanadium are shown.

READING CHECK

4. Name at least three properties of a transition element.

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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


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.


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


The configuration of molybdenum matches the group and period describing its location in 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.

9The Periodic Law

5

B13

Al31

Ga49

In81

Tl

6

C14

Si32

Ge50

Sn82

Pb

7

N15

P33

As51

Sb83

Bi

8

O16

S34

Se52

Te84

Po

9

F17

Cl35

Br53

I

85

At

2

He10

Ne18

Ar36

Kr54

Xe86

Rn

Group 18

Group 13 Group 14 Group 15 Group 16 Group 17

Metals

Metalloids

Nonmetals

The p-Block Elements: Groups 13–18The p-block elements consist of all the elements in Groups 13–18 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 17 - 10 = 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.

READING CHECK

5. What is the group configuration of the elements in Group 17?

Remember!A nonmetal is a poor conductor of electricity and heat. A metalloid, or semiconductor, has some properties of metals and some properties of nonmetals.

Groups 13–18 of the periodic table, which includes the p block and helium.

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

13–18 n s 2 n 1–6 p Number of electrons in np sublevel group number minus 12

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Fluorine

Bromine IodineChlorine

(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 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 ActinidesThe 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 alkaline-earth 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 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

11The Periodic Law

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


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.


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 14 – 10 = 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.

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The configuration of carbon matches the group and period describing its location in 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

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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


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 9 + 1 = 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 10 + 5 + 2 = 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.


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

13The Periodic Law

VOCABULARY1. 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

REVIEW2. 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 Thinking6. 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)?

SECTION 5.2 REVIEW

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SECTION 5.2 Electron Configuration and the Periodic Table

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Transcript of SECTION 5.2 Electron Configuration and the Periodic Table