Periodic table

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The periodic table of the chemical elements is a list known atoms (chemical elements). In the table the elements are placed in the order of their atomic numbers starting with the lowest number. The atomic number of an element is the same as the number of electrons or protons in the atom.

In the periodic table the elements are arranged into periods and groups.

A row of elements across the table is called a period. Each period has a number: from 1 to 7. Period 1 has only 2 elements in it: hydrogen and helium. Period 2 and Period 3 both have 8 elements. Other periods are longer.

A row of elements down the table is called a group. There are 18 groups in the standard periodic table. Each group has a number: from 1 to 18. Elements in a group have electrons arranged in similar ways, which gives them similar chemical properties (they behave in similar ways). For example, group 18 is known as the noble gases because they are all gases and they do not combine with other atoms.

The periodic table can be used by chemists to observe patterns, and relationships between the elements. For example, elements to the top and far left of the table are the most metallic, and elements on the bottom right are the least metallic. (e.g lithium is much more metallic than xenon). There are also many other patterns and relationships.

There are three systems of group numbers; one using Arabic numerals (1,2,3) and the other two using Roman numerals (I, II, III). The Roman numeral names were used at first and are the traditional names; the Arabic numeral names are newer names that the International Union of Pure and Applied Chemistry (IUPAC) decided to use as well. The IUPAC names were meant to replace the older Roman numeral systems as they used the same names to mean different things, which was confusing.

The Periodic Table was invented and arranged by the Russian chemist Dmitri Mendeleev in 1869.

Standard periodic table[edit | edit source]

Group → 1 2
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Period ↓
1 1
H

2
He
2 3
Li
4
Be

5
B
6
C
7
N
8
O
9
F
10
Ne
3 11
Na
12
Mg

13
Al
14
Si
15
P
16
S
17
Cl
18
Ar
4 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
5 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
6 55
Cs
56
Ba
*
71
Lu
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
7 87
 Fr
88
Ra
**
103
Lr
104
Rf
105
Db
106
Sg
107
Bh
108
Hs
109
Mt
110
Ds
111
Uuu
112
Uub
113
Uut
114
Uuq
115
Uup
116
Uuh
117
Uus
118
Uuo

* Lanthanides 57
La
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
** Actinides 89
Ac
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

Chemical Series of the Periodic Table

State at standard temperature and pressure

  • those in blue are gases
  • those in green are liquids
  • those in black are solid

Radioactivity

  • those with solid borders have stable isotopes (Primordial elements)
  • those with dashed borders have only radioactive naturally occurring isotopes
  • those with dotted borders do not occur naturally (Synthetic Elements)
  • those without borders are too radioactive to have been discovered yet

Other methods for displaying the chemical elements[edit | edit source]

See also[edit | edit source]

External links[edit | edit source]

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