5 Steps to a 5 AP Chemistry

into thin sheets (malleable) and extruded into wires (ductile). Chemically, metals tend to

lose electrons in reactions, to form cations.

Elements bordering the stair-stepped line (B, Si, Ge, As, Sb, Te) are classified as metal-

loids. Metalloidshave properties of both metals and nonmetals. Their unusual electrical

properties make them valuable in the semiconductor and computer industry.

The rest of the elements, to the right of the metalloids, are called nonmetals.

Nonmetalshave properties that are often the opposite of metals. Some are gases, are poor

conductors of heat and electricity, are neither malleable nor ductile, and tend to gain elec-

trons in their chemical reactions to form anions.

Another way to group the elements on the periodic table is in terms of periods and

groups (families). Periodsare the horizontal rows, which have consecutive atomic numbers.

The periods are numbered from 1 to 7. Elements in the same period do not have similar

properties in terms of reactions.

The vertical rows on the periodic table are called groupsor families. They may be

labeled in one of two ways. An older and still widely used system is to label each group with

a Roman numeral and a letter, A or B. The groups that are labeled with an A are called the

main-group elements, while the B groups are called the transition elements. Two other

horizontal groups, the inner transition elements, have been pulled out of the main body

of the periodic table. The Roman numeral at the top of the main-group families indicates

the number of valence(outermost shell) electrons in that element. Valence electrons are

normally considered to be only the s and p electrons in the outermost energy level. The

transition elements (B groups) are filling d-orbitals, while the inner transition elements are

filling f-orbitals.

Basics  51

Periodic Table of the Elements

Periods

1 18

1

2 13 14 15 16 17

2

3

3 45 6 789 10 11 12

IA IIA IIIB IVB VB VIB VIIB VIIIB IB IIB IIIA IVA VA VIA VIIA 0

4

5

6

7

1

1.0080H

1

H

1.0080

Atomic number

Symbol

Atomic Mass

3

6.941Li

4

9.01218Be

11

Na

22.9898

2

4.00260He

10

20.179Ne

18

Ar

39.948

9

18.9984F

17

Cl

35.453

8

15.9994O

16

S

32.06

7

14.0067N

15

P

30.9738

6

12.011C

14

Si

28.086

5

10.81B

13

Al

26.9815

12

Mg

24.305

19

39.102K

20

40.08Ca

37

85.4678Rb

38

87.62Sr

55

132.9055Cs

56

137.34Ba

87

Fr

(223)

88

Ra

226.0254

21

44.9559Sc

22

47.90Ti

39

88.9059Y

40

91.22Zr

57

138.9055La

72

178.49Hf

89

Ac

(227)

104

Unq

(261)

23

50.9414V

24

51.996Cr

41

92.9064Nb

42

Mo95.94

73

180.9479Ta

74

183.85W

105

Unp

(262)

106

Unh

(263)

25

54.9380Mn

26

55.847Fe

43

98.9062Tc

44

101.07Ru

75

186.2Re

76

190.2Os

27

58.9332Co

28

58.71Ni

45

102.9055Rh

46

106.4Pd

77

192.22Ir

78

195.09Pt

29

63.546Cu

47

107.868Ag

79

196.9665Au

30

65.37Zn

48

112.40Cd

80

200.59Hg

31

69.72Ga

49

114.82In

81

204.37Tl

32

72.59Ge

50

118.69Sn

82

207.2Pb

33

74.9216As

51

121.75Sb

83

208.9806Bi

34

78.96Se

52

127.60Te

84

(210)Po

35

79.904Br

53

126.9045I

85

(210)At

58

Ce

140.12

59

Pr

140.9077

60

Nd

144.24

61

Pm

(145)

62

Sm

150.4

63

Eu

151.96

64

Gd

157.25

65

Tb

158.9254

66

Dy

162.50

67

Ho

164.9303

68

Er

167.26

69

Tm

168.9342

70

Yb

173.04

71

Lu

174.97

90

232.0381Th

91

231.0359Pa

92

238.029U

93

237.0482Np

94

(242)Pu

95

Am(243)

96

Cm(247)

97

(249)Bk

98

(251)Cf

99

(254)Es

100

(253)Fm

101

Md(256)

102

No(254)

103

(257)Lr

36

83.80Kr

54

131.30Xe

86

(222)Rn

Modern
group
numbers

Classical
group
numbers

*

†

*

†

Figure 5.4 The periodic table.