Periodic table of elements
18
1
1
1
Rows in the table represent the periods and get longer as the atomic
numbers increase. The number of electrons increase from left to right
across the table. There are eighteen groups represented by columns
in the table; these groups have chemical features in common and
have the same number of electrons in the outer orbit of the atoms.
Most of the elements are metals with the non-metals occurring more
frequently in groups thirteen to eighteen. Groups one to twelve are
exclusively metals and on the boundary between the two are
metalloids which display properties of both metals and non-metals.
Some of the groups have collective names: group one are the alkali
metals; group two are the alkaline earth metals; group eleven are the
coinage metals; group seventeen are the halogens; and group
eighteen are the noble gases. The first widely recognised table was
published in 1869 by the Russian chemist Dmitri Mendeleev.
1
H
Hydrogen
2
1.0079
3
2
Li
2
1
9.0122
6.9410
3
Na
2
8
1
Sodium
4
K
2
8
8
1
Rb
2
8
18
8
1
85.4680
6
Cs
Cesium
2
8
18
18
8
1
7
Fr
Francium
(223.0000)
20
Ca
2
8
8
2
38
Sr
2
8
18
8
2
Sc
2
8
18
32
18
8
1
88
Ra
Radium
V
44.9560
47.8670
50.9420
39
Y
2
8
18
9
2
40
Zr
2
8
18
10
2
Zirconium
91.2240
72
E57 - E71
Hf
Hafnium
2
8
18
32
10
2
104
E89 - E103
Rf
Rutherfordium
226.0300
2
8
18
32
32
10
2
261.1100
57
La
Lanthanium
2
8
18
18
9
2
138.9100
89
Ac
Actinium
(227.0000)
58
Ce
Cerium
90
Th
Thorium
232.0381
2
8
11
2
Gas
element
2
8
18
7
35
Br
Bromine
79.9040
Atomic weight (of
most stable isotope
when in brackets)
2
8
18
20
8
2
Cr
2
8
13
1
51.9960
2
8
18
12
1
42
2
8
18
13
1
25
54.9380
55.8450
43
Technetium
92.9060
95.9400
(98.0000)
Ta
Tantalum
105
Db
Dubnium
59
Pr
Praseodyium
91
Pa
Protactinium
231.0359
74
W
Tungsten
2
8
18
32
12
2
183.8400
2
8
18
32
32
11
2
106
Sg
Seaborgium
60
Nd
Neodymium
2
8
18
22
8
2
144.2400
2
8
18
32
20
9
2
92
U
Uranium
238.0300
Re
Rhenium
107
Bh
Bohrium
61
Ru
2
8
14
2
2
8
18
32
13
2
76
Os
Osmium
108
Hs
Hassium
2
8
18
15
1
62
45
Rh
77
Ir
Iridium
109
Mt
Meitnerium
93
Np
Neptunium
237.0500
Samarium
2
8
18
24
8
2
63
94
Pu
Plutonium
(244.0000)
Europium
2
8
18
32
24
8
2
95
46
Pd
2
8
18
32
32
15
2
2
8
18
18
47
Ag
Palladium
Silver
106.4200
107.8700
78
Pt
Platinum
2
8
18
32
17
1
Helium
14
13
5
B
2
3
Boron
13
Al
110
Ds
Darmstadium
64
Gd
Gadolinium
96
79
Au
Gold
2
8
18
32
32
16
2
111
Rg
Roentgenium
65
Tb
Terbium
97
Am Cm Bk
Americium
(243.0000)
Curium
(247.0000)
2
8
18
18
1
2
8
18
32
18
1
2
8
3
Berkelium
(247.0000)
48
2
8
18
32
32
17
2
2
8
18
18
2
49
Cd In
Cadmium
Indium
112.4100
114.8200
80
Hg
Mercury
2
8
18
32
18
2
112
Cn
Copernicium
66
Dy
Dysprosium
98
Cf
Californium
(251.0000)
2
8
18
3
81
Tl
Thallium
2
8
18
18
3
2
8
18
32
32
18
2
113
2
8
18
32
18
3
2
8
18
32
32
18
3
67
Ho
Holmium
99
Es
Einsteinium
(252.0000)
2
8
18
4
As
Arsenic
72.6400
74.9220
50
Sn
2
8
18
18
4
82
Pb
Lead
2
8
18
32
18
4
114
Flerovium
68
Er
Erbium
100
2
8
5
51
Sb
2
8
18
32
32
18
4
2
8
18
5
34
Se
52
Te
Antimony
Tellurium
121.7600
127.6000
83
Bi
Bismuth
115
2
8
18
32
18
5
84
Po
Polonium
69
2
8
18
32
32
18
5
116
Livermorium
2
8
18
31
8
2
70
101
Ytterbium
102
Fm Md No
Fermium
(257.0000)
Mendelevium
(258.0000)
Nobelium
(259.0000)
Cl
2
8
18
18
6
2
8
18
32
18
6
2
8
7
35.4530
39.9480
35
Br
2
8
18
7
53
I
36
Kr
2
8
18
18
7
54
Xe
Xenon
126.9000
131.2900
At
Astatine
117
2
8
18
32
18
7
86
Rn
Radon
71
Lu
Lutetium
103
Lr
Lawrencium
(262.0000)
2
8
18
18
8
2
8
18
32
18
8
222.0000
2
8
18
32
32
18
7
118
Uus Uuo
Ununseptium
2
8
18
8
83.8000
Iodine
85
2
8
8
Krypton
Ununoctium
(294.0000)
2
8
18
32
9
2
174.9700
0
18
32
32
8
2
Ar
Argon
(294.0000)
2
8
18
32
8
2
18
Chlorine
(210.0000)
2
8
18
32
32
18
6
Ne
2
8
20.1797
79.9040
173.0400
2
8
18
32
31
8
2
17
10
Neon
Bromine
(293.0000)
Tm Yb
Thulium
2
8
18
6
(209.0000)
Uup Lv
Ununpentium
2
8
6
78.9600
2
8
18
18
5
2
7
18.9984
Selenium
168.9300
2
8
18
32
30
8
2
S
4.0026
Fluorine
32.0650
(288.0000)
2
8
18
30
8
2
16
9
F
Sulphur
208.9800
167.2600
2
8
18
32
29
8
2
33
Germanium
(289.0000)
2
8
18
29
8
2
P
O
2
6
15.9994
30.9738
207.2000
164.9300
2
8
18
32
28
8
2
Ge
15
8
17
Oxygen
Phosphorus
118.7100
(284.0000)
2
8
18
28
8
2
32
Uut Fl
Ununtrium
2
8
4
Tin
204.3800
162.5000
2
8
18
32
27
8
2
Ga
Si
N
2
5
14.0070
28.0855
69.7230
(285.0000)
2
8
18
27
8
2
31
14
7
Nitrogen
Silicon
Gallium
200.5900
158.9300
2
8
18
32
25
9
2
Zn
2
8
18
2
C
2
4
12.0107
26.9815
65.3900
(280.0000)
2
8
18
25
9
2
30
6
16
15
Carbon
10.8110
Zinc
196.9700
157.2500
2
8
18
32
25
8
2
Cu
2
8
18
1
63.5460
(281.0000)
2
8
18
25
8
2
29
2
He
12
Copper
195.0800
151.9600
150.3600
2
8
18
32
23
8
2
2
8
18
32
15
2
266.1400
Pm Sm Eu
Promethium
2
8
18
16
1
192.2200
2
8
18
32
32
14
2
Ni
2
8
16
2
58.6930
102.9100
2
8
18
32
14
2
28
11
Nickel
Rhodium
264.1300
2
8
18
23
8
2
Co
2
8
15
2
58.9330
190.2300
2
8
18
32
32
13
2
27
10
Cobalt
101.0700
(145.0000)
2
8
18
32
20
9
2
44
9
Ruthenium
262.1200
226.0300
2
8
18
21
8
2
75
2
8
18
14
1
186.2100
2
8
18
32
32
12
2
26
Iron
Molybdenum
2
8
18
32
11
2
2
8
13
2
Manganese
Niobium
73
8
Mn Fe
Nb Mo Tc
140.9100
2
8
18
32
18
10
2
24
7
Chromium
262.1100
140.1200
2
8
18
32
18
9
2
41
6
180.9500
178.4900
2
8
18
32
18
8
2
23
Vanadium
88.9060
Barium
Ti
2
8
10
2
Titanium
87.6200
Ba
22
5
Scandium
Yttrium
2
8
18
18
8
2
2
8
9
2
21
Strontium
56
4
137.3300
132.9100
87
3
40.0780
Rubidium
55
Liquid
element
2
Aluminium
Calcium
39.0980
5
Mg
2
8
2
24.3050
Potassium
37
12
Alkali metals
Alkaline earth metals
Transition metals
Other metals
Other non-metals
Halogens
Inert gases
Lanthanides
Actinides
Trans-actinides
(Manmade atoms
that exist for less
than a second)
Radioactive
element
Magnesium
22.9898
19
Be
2
2
Beryllium
Lithium
11
4
Atomic number
(number of protons
in an atom)
Chemical
formula
Number of
electrons
orbiting in
each shell
2
8
18
32
32
9
2
2
8
18
32
32
18
8