SUPPLEMENT 6 S39

is placed by itself above the center of the table

because it does not fi t very well into any of the

groups

The elements arranged in a diagonal staircase

pattern between the metals and nonmetals have

a mixture of metallic and nonmetallic properties

and are called metalloids.

Figure 1 also identifi es the elements required

as nutrients (black squares) for all or some forms

of life and elements that are moderately or

highly toxic (red squares) to all or most forms

of life. Six nonmetallic elements—carbon (C),

oxygen (O), hydrogen (H), nitrogen (N), sulfur

(S), and phosphorus (P)—make up about 99%

of the atoms of all living things.

THINKING ABOUT

The Periodic Table

Use the periodic table to identify by name and

symbol two elements that should have chemical

properties similar to those of (a) Ca, (b) potas-

sium, (c) S, (d) lead.

atomic number 11) with 11 positively charged

protons and 11 negatively charged electrons

can lose one of its electrons. It then becomes

a sodium ion with a positive charge of 1 (Na)

because it now has 11 positive charges (protons)

but only 10 negative charges (electrons).

Nonmetals, found in the upper right of the

table, do not conduct electricity very well. Ex-

amples are hydrogen (H), carbon (C), nitrogen

(N), oxygen (O), phosphorus (P), sulfur (S),

chlorine (Cl), and fl uorine (F).

Atoms of some nonmetals such as chlo-

rine, oxygen, and sulfur tend to gain one or

more electrons lost by metallic atoms to form

negatively charged ions such as O^2 , S^2 , and

Cl. For example, an atom of the nonmetallic

element chlorine (Cl, with atomic number 17)

can gain an electron and become a chlorine ion.

The ion has a negative charge of 1 (Cl) because

it has 17 positively charged protons and 18

negatively charged electrons. Atoms of nonmet-

als can also combine with one another to form

molecules in which they share one or more

pairs of their electrons. Hydrogen, a nonmetal,

Chemists Use the Periodic
Table to Classify Elements
on the Basis of Their
Chemical Properties

Chemists have developed a way to classify the
elements according to their chemical behavior,
in what is called the periodic table of elements
(Figure 1). Each horizontal row in the table is
called a period. Each vertical column lists ele-
ments with similar chemical properties and is
called a group.
The partial periodic table in Figure 1 shows
how the elements can be classifi ed as metals,
nonmetals, and metalloids. Most of the elements
found to the left and at the bottom of the table
are metals, which usually conduct electricity and
heat, and are shiny. Examples are sodium (Na),
calcium (Ca), aluminum (Al), iron (Fe), lead
(Pb), silver (Ag), and mercury (Hg).
Atoms of metals tend to lose one or more of
their electrons to form positively charged ions
such as Na, Ca^2 , and Al^3 . For example, an
atom of the metallic element sodium (Na, with

Some Basic Chemistry

(Chapters 1–5)

SUPPLEMENT

6

3

Li

lithium

4

Be

beryllium

11

Na

sodium

12

Mg

magnesium

2

He

helium

10

Ne

neon

18

Ar

argon

36

Kr

krypton

54

Xe

xenon

86

Rn

radon

9

F

fluorine

17

Cl

chlorine

35

Br

bromine

53

I

iodine

85

At

astatine

8

O

oxygen

16

S

sulfur

34

Se

selenium

52

Te

tellurium

84

Po

polonium

7

N

nitrogen

15

P

phosphorus

33

As

arsenic

51

Sb

antimony

83

Bi

bismuth

6

C

carbon

14

Si

silicon

32

Ge

germanium

50

Sn

tin

82

Pb

lead

5

B

boron

13

Al

aluminum

31

Ga

gallium

30

Zn

zinc

29

Cu

copper

28

Ni

nickel

27

Co

cobalt

26

Fe

iron

25

Mn

manganese

24

Cr

chromium

23

V

vanadium

22

Ti

titanium

21

Sc

scandium

20

Ca

calcium

19

K

potassium

48

Cd

cadmium

47

Ag

silver

46

Pd

palladium

45

Rh

rhodium

44

Ru

ruthenium

43

Tc

technetium

42

Mo

molybdenum

41

Nb

niobium

40

Zr

zirconium

39

Y

yttrium

38

Sr

strontium

37

Rb

rubidium

80

Hg

mercury

79

Au

gold

78

Pt

platinum

77

Ir

iridium

76

Os

osmium

75

Re

rhenium

74

W

tungsten

73

Ta

tantalum

72

Hf

hafnium

57

La

lanthanum

56

Ba

barium

55

Cs

cesium

49

In

indium

81

Tl

thallium

1

H

hydrogen

Group

IA IIA

IIIB IVB VB VIB VIIB VIIIB IB IIB

IIIA IVA VA VIA VIIA

VIIIA

Atomic number

Symbol

Name

Metals

Required for

all or some

life-forms

Nonmetals

Metalloids

1

H

hydrogen

Moderately

to highly

toxic

80

Hg

mercury

Figure 1 Abbreviated periodic table of elements. Elements in the same vertical column, called a group, have similar
chemical properties. To simplify matters at this introductory level, only 72 of the 118 known elements are shown.