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HOW DOES THE PERIODIC TABLE WORK?

The periodic table sets out the elements in a way that highlights similarities and

trends in their properties. Elements in the same group (column) have similar

properties. The properties change gradually along periods (rows) in the table –

elements on the left are metals, elements on the right are non-metals. As you

move across periods, the atomic number increases. Also, at the start of a period,

elements have one electron in their outer shell – by the end, they have eight.

The periodic table is a simple list of all the elements. The elements

are arranged by their atomic number. The information given for

each element includes atomic number, symbol, name, and mass

number. The vertical columns of the table are called groups, and

the horizontal rows are called periods.

WHAT IS AN ISOTOPE?

All elements have several forms called isotopes.

Each isotope of an element has the same atomic

number, but a different atomic mass. In carbon,

99 per cent of the atoms are isotope carbon 12,

and 1 per cent are carbon 13. Both isotopes have

six protons, but carbon 12 has six neutrons,

while carbon 13 has seven.

WHY IS THE PERIODIC TABLE USEFUL?

Scientists can tell a great deal about the

properties of an element, even before they do

experiments, by looking at its position in the

periodic table. They can decide whether it will be

a metal or a non-metal, judge how well it will

conduct electricity, and predict how it will react

with other elements.

WHY ARE ELEMENTS IN A GROUP SIMILAR?

The chemical properties of an element depend on the

number of electrons in its outer shell. Elements in the

same group have the same number of outer electrons.

For example, all the elements in Group 1 (alkali

metals) have one electron in their outer shells. They

are all silvery-white, highly reactive metals.

1 PERIODIC TABLE
Russian chemist Dimitri Ivanovich
Mendeleyev (1834–1907) drew up the
first periodaic table in 1869. Gaps in
Mendeleyev’s table suggested the existence
of elements that were not known at the
time. The missing elements have all since
been discovered – for example, scandium,
gallium, and germanium.

PERIODIC TABLE

The mass number gives the number

of protons and neutrons in the

nucleus. The mass numbers given on

this page are for the most common

isotope (form) of the element

The symbol is used as

shorthand for the element

in chemical equations

The atomic number

is the number of protons

in the nucleus

Alkali metals

Alkaline earth metals

Transition metals

Rare earths

Radioactive rare earths

Other metals

Semimetals

Non-metals

Noble gases

Hydrogen does

not belong to any

one group

Undefined

79

Au

Gold

197

KEY

1

H

Hydrogen

1

3

Li

Lithium

7

4

Be

Beryllium

9

11

Na

Sodium

23

12

Mg

Magnesium

24

19

K

Potassium

39

20

Ca

Calcium

40

37

Rb

Rubidium

85

38

Sr

Strontium

88

55

Cs

Caesium

133

56

Ba

Barium

138

87

Fr

Francium

223

88

Ra

Radium

226

57-71

89-103

21

Sc

Scandium

45

39

Y

Yttrium

89

22

Ti

Titanium

48

40

Zr

Zirconium

90

72

Hf

Hafnium

180

104

Rf

Rutherfordium

261

23

V

Vanadium

51

41

Nb

Niobium

93

73

Ta

Tantalum

181

105

Db

Dubnium

262

24

Cr

Chromium

52

42

Mo

Molybdenum

98

74

W

Tungsten

184

25

Mn

Manganese

55

43

Tc

Technetium

97

75

Re

Rhenium

187

107

Bh

Bohrium

264

26

Fe

Iron

56

44

Ru

Ruthenium

102

76

Os

Osmium

192

108

Hs

Hassium

267

27

Co

Cobalt

59

45

Rh

Rhodium

103

77

Ir

Iridium

193

109

Mt

Meitnerium

268

28

Ni

Nickel

58

46

Pd

Palladium

106

78

Pt

Platinum

195

29

Cu

Copper

63

47

Ag

Silver

107

79

Au

Gold

197

30

Zn

Zinc

64

48

Cd

Cadmium

11 4

80

Hg

Mercury

202

31

Ga

Gallium

69

49

In

Indium

11 5

81

Ti

Thallium

205

32

Ge

Germanium

74

50

Sn

Tin

120

82

Pb

Lead

208

33

As

Arsenic

75

51

Sb

Antimony

121

83

Bi

Bismuth

209

34

Se

Selenium

80

52

Te

Tellurium

130

84

Po

Polonium

209

35

Br

Bromine

79

53

I

Iodine

127

85

At

Astatine

210

36

Kr

Krypton

84

13

Al

Aluminium

27

14

Si

Silicon

28

15

P

Phosphorus

31

16

S

Sulphur

32

17

Cl

Chlorine

35

18

Ar

Argon

40

5

B

Boron

11

6

C

Carbon

12

7

N

Nitrogen

14

8

O

Oxygen

16

9

F

Fluorine

19

10

Ne

Neon

20

2

He

Helium

4

54

Xe

Xenon

132

86

Rn

Radon

222

89

Ac

Actinium

227

90

Th

Thorium

232

91

Pa

Protactinium

231

92

U

Uranium

238

93

Np

Neptunium

237

94

Pu

Plutonium

244

95

Am

Americium

243

96

Cm

Curium

247

97

Bk

Berkelium

247

98

Cf

Californium

251

99

Es

Einsteinium

254

100

Fm

Fermium

257

101

Md

Mendelevium

258

102

No

Nobelium

255

103

Lr

Lawrencium

256

57

La

Lanthanum

139

58

Ce

Cerium

140

59

Pr

Praseodymium

141

60

Nd

Neodymium

142

61

Pm

Promethium

145

62

Sm

Samarium

152

63

Eu

Europium

153

64

Gd

Gadolinium

158

65

Tb

Terbium

159

66

Dy

Dysprosium

164

67

Ho

Holmium

165

68

Er

Erbium

168

69

Tm

Thulium

169

70

Yb

Ytterbium

174

71

Lu

Lutetium

175

106

Sg

Seaborgium

268

110

Ds

Darmstadtium

281

111

Rg

Roentgenium

281

11 3

Uut

Ununtrium

284

11 4

Uuq

Ununquadium

289

11 5

Uup

Ununpentium

288

11 6

Uuh

Ununhexium

293

(117)

(Uus)

(Ununseptium)

(not known)

11 8

Uuo

Ununoctium

294

11 2

Cn

Copernicium

285

Elements