

National Chemistry Week, October 19-24, 2009 NCW kicks off this week with the theme "Chemistry—It's Elemental!" Visit www.acs.org/ncw for more information.

THE PERIODIC TABLE OF THE ELEMENTS 1

H

2

He 3

Li 4

Be

5

B 6

C 7

N 8

O 9

F 10

Ne 11

Na 12

Mg

13

Al 14

Si 15

P 16

S 17

Cl 18

Ar 19

K 20

Ca 21

Sc 22

Ti 23

V 24

Cr 25

Mn 26

Fe 27

Co 28

Ni 29

Cu 30

Zn 31

Ga 32

Ge 33

As 34

Se 35

Br 36

Kr 37

Rb 38

Sr 39

Y 40

Zr 41

Nb 42

Mo 43

Tc 44

Ru 45

Rh 46

Pd 47

Ag 48

Cd 49

In 50

Sn 51

Sb 52

Te 53

I 54

Xe 55

Cs 56

Ba 57*

La 72

Hf 73

Ta 74

W 75

Re 76

Os 77

Ir 78

Pt 79

Au 80

Hg 81

Tl 82

Pb 83

Bi 84

Po 85

At 86

Rn 87

Fr 88

Ra 89**

Ac 104

Rf 105

Db 106

Sg 107

Bh 108

Hs 109

Mt 110

Ds 111

Uuu 112

Uub

114

Uuq



* Lanthanide series 58

Ce 59

Pr 60

Nd 61

Pm 62

Sm 63

Eu 64

Gd 65

Tb 66

Dy 67

Ho 68

Er 69

Tm 70

Yb 71

Lu

** Actinide series

90

Th 91

Pa 92

U 93

Np 94

Pu 95

Am 96

Cm 97

Bk 98

Cf 99

Es 100

Fm 101

Md 102

No 103

Lr



NOTE: Yellow indicates alkali and alkaline earth metals; tan, transition metals; blue, main-group elements; gray, noble gases; and orange, lanthanide and actinide series

EDITOR'S NOTE C&EN has received numerous letters praising this special issue, The Periodic Table (Sept. 8), and inquiring how to obtain multiple copies for classroom use. The entire issue is on the Web free of charge at http://www.cen-online.org. Click on the C&EN 80th anniversary icon. Bulk copies of the special issue are also available. Single issues cost $22 each. 10 or more cost $11 each. Direct inquiries to Margaret Neville, m_neville@acs.org, or Sandra Tinker, s_tinker@acs.org. An individual free copy is available to teachers by sending an e-mail to pss@acs.org.

RUDY BAUM , C&EN WASHINGTON

T he Periodic Table is natures rosetta stone. To the uninitiated, its just 100-plus numbered boxes, each containing one or two letters, arranged with an odd, skewed symmetry. To chemists, however, the periodic table reveals the organizing principles of matter, which is to say, the organizing principles of chemistry. At a fundamental level, all of chemistry is contained in the periodic table.

Thats not to say, of course, that all of chemistry is obvious from the periodic table. Far from it. But the structure of the table reflects the electronic structure of the elements, and hence their chemical properties and behavior. Perhaps it would be more appropriate to say that all of chemistry starts with the periodic table. What has always struck me as remarkable about Dmitry Mendeleyevs discovery in 1869 of a way to arrange the elements known at that time into a meaningful and predictive periodic table is that he accomplished it without any knowledge of the structure of atoms. There are no atomic numbers on Mendeleyevs periodic table, only atomic weights and the groupings of elements based on their known properties. More than 30 years would pass before J. J. Thomson (who discovered the electron) suggested that the electronic configuration of atoms might account for the periodicity of the elements, and more than 40 years would pass before atomic numbers were recognized as the basis for ordering the elements.



Indeed, as John Emsley notes in his invaluable book, Natures Building Blocks: An AZ Guide to the Elements, Mendeleyev never accepted that electrons came from atoms because he was convinced that atoms were indivisible.



No matter. Mendeleyevs brilliant insight propelled chemistry into the 20th century. New elements were discovered that filled in the holes Mendeleyev left in his table, and their atomic weights and chemical properties corresponded with remarkable accuracy to Mendeleyevs predictions. And as the revolution in chemistry and physics unfolded in the early decades of the 20th century, most of the discoveries about the structure of atoms, their properties, and how they interact with each other made perfect sense in light of the periodic table.



The periodic table is so central to chemistry that it seemed natural to devote a special issue to it and the elements that compose it as we celebrate C&ENs 80th anniversary. The 89 essays are delightfully varied. We hope they will give you a new perspective on and appreciation of the building blocks of our science.











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