The Foundations of Chemistry

Because the noble gases form few
compounds, they are not included in
this discussion.

250 CHAPTER 6: Chemical Periodicity

36 electrons more tightly, and Br
is smaller than Se^2 
. Te^2 
has electrons in the fifth main

shell (outer configuration of 5s^25 p^6 ), so it is larger than either of the other two ions.

Br
Se^2 
Te^2 

You should now work Exercises 38 and 40.

ELECTRONEGATIVITY

The electronegativity (EN)of an element is a measure of the relative tendency of an

atom to attract electrons to itself when it is chemically combined with another atom.

Elements with high electronegativities (nonmetals) often gain electrons to form

anions. Elements with low electronegativities (metals) often lose electrons to form

cations.

Electronegativities of the elements are expressed on a somewhat arbitrary scale, called the

Pauling scale (Table 6-3). The electronegativity of fluorine (4.0) is higher than that of any

other element. This tells us that when fluorine is chemically bonded to other elements,

6-6

H

2.1

1

Li

1.0

3

Na

1.0

11

K

0.9

19

Rb

0.9

37

Cs

0.8

55

Fr

0.8

87

Be

1.5

4

Mg

1.2

12

Ca

1.0

20

Sr

1.0

38

Ba

1.0

56

Ra

1.0

88

Sc

1.3

21

Y

1.2

39

La

1.1

57

Ac

1.1

89

Ti

1.4

22

Zr

1.3

40

Hf

1.3

72

V

1.5

23

Nb

1.5

41

Ta

1.4

73

Cr

1.6

24

Mo

1.6

42

W

1.5

74

Mn

1.6

25

Tc

1.7

43

Re

1.7

75

Fe

1.7

26

Ru

1.8

44

Os

1.9

76

Co

1.7

27

Rh

1.8

45

Ir

1.9

77

Ni

1.8

28

Pd

1.8

46

Pt

1.8

78

Cu

1.8

29

Ag

1.6

47

Au

1.9

79

Zn

1.6

30

Cd

1.6

48

Hg

1.7

80

B

2.0

5

Al

1.5

13

Ga

1.7

31

In

1.6

49

Tl

1.6

81

C

2.5

6

Si

1.8

14

Ge

1.9

32

Sn

1.8

50

Pb

1.7

82

N

3.0

7

P

2.1

15

As

2.1

33

Sb

1.9

51

Bi

1.8

83

O

3.5

8

S

2.5

16

Se

2.4

34

Te

2.1

52

Po

1.9

84

F

4.0

9

Cl

3.0

17

Br

2.8

35

I

2.5

53

At

2.1

85

He

2

Ne

10

Ar

18

Kr

36

Xe

54

Rn

86

1 2 3 4 5 6 7

IIIB IVB VB VIB VIIB IB IIB

IIIA IVA VA VIA VIIA

VIIIA

VIIIB

Ce

1.1

58

Pr

1.1

59

Nd

1.1

60

Pm

1.1

61

Sm

1.1

62

Eu

1.1

63

Gd

1.1

64

Tb

1.1

65

Dy

1.1

66

Ho

1.1

67

Er

1.1

68

Tm

1.1

69

Yb

1.0

70

Lu

1.2

71

Th

1.2

90

Pa

1.3

91

U

1.5

92

Np

1.3

93

Pu

1.3

94

Am

1.3

95

Cm

1.3

96

Bk

1.3

97

Cf

1.3

98

Es

1.3

99

Fm

1.3

100

Md

1.3

101

No

1.3

102

Lr

1.5

103

*

†

*

†

IIA

IA

Metals

Nonmetals

Metalloids

TABLE 6-3 Electronegativity Values of the Elements a

aElectronegativity values are given at the bottoms of the boxes.