14
Introduction
Periodic table
of elements
The periodic table is a useful way of organizing the elements.
It arranges the elements in order of their atomic number,
which is the number of protons in the nucleus of an atom,
and is unique to every element. The table also divides the
elements into rows, called “periods”, and columns, called
“groups”. Dmitri Mendeleev, the chemist who devised the
table, arranged the elements based on the similarity of
certain physical and chemical properties.
Sc
21
44.
Y
39
88.
La-Lu
57-
Ac-Lr
89-
Zr
40
91.
Hf
72
178.
Rf
104
(261)
La
57
138.
Ac
89
(227)
Ti
22
47.
Nb
41
92.
Ta
73
180.
Db
105
(262)
Ce
58
140.
Th
90
232.
V
23
50.
Mo
42
95.
W
74
183.
Sg
106
(266)
Pr
59
140.
Pa
91
231.
Cr
24
51.
Tc
43
(96)
Re
75
186.
Bh
107
(264)
Nd
60
144.
U
92
238.
Mn
25
54.
Ru
44
101.
Os
76
190.
Hs
108
(277)
Pm
61
(145)
Np
93
(237)
Fe
26
55.
Rh
45
102.
Ir
77
192.
Mt
109
(268)
Sm
62
(150.36)
Pu
94
(244)
Co
27
58.
Pd
46
106.
Pt
78
195.
Ds
110
(281)
Eu
63
151.
Am
95
(243)
Ni
28
58.
Ag
47
107.
Au
79
196.
Rg
111
(272)
Gd
64
157.
Cm
96
(247)
Cu
29
63.
Zn
30
Cd
48
Hg
80
Tb
65
Cn
112
Bk
97
112.
200.
285
158.
(247)
65.
H
1
1.
Li
3
6.
Na
11
22.
K
19
39.
Rb
37
85.
Cs
55
132.
Fr
87
(223)
Be
4
9.
Mg
12
24.
Ca
20
40.
Sr
38
87.
Ba
56
137.
Ra
88
(226)
The actinides and the
lanthanides are placed
between the alkaline earth
metals and the transition
metals, but have been
moved below to give
them more space.
014-015_Periodic_Table.indd 14 12/12/16 5:37 pm