Periodic table

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The periodic table of the chemical elements, also called the Mendeleev periodic table, is a tabular display of the known chemical elements. First created by Dmitri Mendeleev, the elements are arranged by electron structure so that many chemical properties vary regularly across the table. Each element is listed by its atomic number and chemical symbol. Mendeleev's discovery of the periodic table was one of the greatest developments in modern chemistry; chemists for the first time were able to quantitatively explain the behaviour of the elements and to predict the existence of undiscovered ones. There are 116 chemical elements whose discovery has been confirmed; 94 can be found naturally on Earth, and the rest have been produced in laboratories.

The standard table provides the necessary basics. There are also other methods for displaying the chemical elements for more details or different perspectives.

1 Groups
- 1.1 Group numbers
- 1.2 Standard periodic table
2 Other methods for displaying the chemical elements
3 Periodicity of chemical properties
4 Explanation of the structure of the periodic table
5 History
6 Further resources
7 See also
8 External links

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Groups

A group is a vertical column in the periodic table of the elements. There are 18 groups in the standard periodic table. Elements in a group have similar configurations of their valence shell electrons, which gives them similar properties.

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Group numbers

There are three systems of group numbers; one using Arabic numerals, another using Roman numerals, and one using a combination of Roman numerals and Latin letters. The Roman numeral names are the original traditional names of the groups; the Arabic numeral names are a newer naming scheme recommended by the International Union of Pure and Applied Chemistry (IUPAC). The IUPAC scheme was developed to replace both older Roman numeral systems as they confusingly used the same names to mean different things.

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Standard periodic table

Group →

↓ Period

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

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

104
Rf

105
Db

106
Sg

107
Bh

108
Hs

109
Mt

110
Ds

111
Rg

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

71
Lu

** 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

103
Lr

Chemical series of the periodic table
Alkali metals²	Alkaline earth metals²	Lanthanides^1,²	Actinides^1,²	Transition metals²
Poor metals	Metalloids	Nonmetals	Halogens³	Noble gases³

¹Actinides and lanthanides are collectively known as "Rare Earth Metals".

²Alkali metals, alkaline Earth metals, transition metals, actinides, and lanthanides are all collectively known as "Metals". ³Halogens and noble gases are also non-metals.

State at standard temperature and pressure

those with atomic number in red are gases at standard temperature and pressure (STP)
those with atomic number in blue are liquids at STP
those with atomic number in black are solid at STP

Natural occurrence

those with solid borders have isotopes that are older than the Earth (Primordial elements)
those with dashed borders naturally arise from decay of other chemical elements and have no isotopes older than the earth
those with dotted borders are made artificially (Synthetic elements)
those without borders have not been discovered yet

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Other methods for displaying the chemical elements

The standard table (same as above) provides the basics.
A vertical table for improved readablity in web browsers.
The big table provides the basics plus full element names.
The huge table provides the basics plus full element names and atomic masses.
A table with an inline F-block inserts the Lanthanides and Actinides back into the table.
The elements to 218 suggests the places so-far undiscovered elements would be.
The Chemical Galaxy groups elements according to their electron configuration (chemical characteristics), and provides the atomic number.
Electron Configurations
Metals and Non Metals
Periodic table filled by blocks
Table in Chinese
List of elements by name
List of elements by symbol
List of elements by atomic number
List of elements by boiling point
List of elements by melting point
List of elements by density
List of elements by atomic mass

And here is the periodic table for magnetic resonance.

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Periodicity of chemical properties

Elements adjacent to one another within a group have similar physical properties, despite their significant differences in mass. Elements adjacent to one another within a period have similar mass but different properties.

For example, very near to nitrogen (N) in the second period of the chart are carbon (C) and oxygen (O). Despite their similarities in mass (they differ by only a few atomic mass units), they have extremely different properties, as can be seen by looking at their allotropes: diatomic oxygen is a gas that supports burning, diatomic nitrogen is a gas that does not support burning, and carbon is a solid which can be burned. (Yes, diamonds can be burned!)

In contrast, very near to chlorine (Cl) in the next-to-last group in the chart (the halogens) are fluorine (F) and bromine (Br). Despite their dramatic differences in mass, their allotropes have very similar properties. They are all highly corrosive (meaning they combine readily with metals to form metal halide salts); chlorine and fluorine are gases, while bromine is a very low-boiling liquid; chlorine and bromine are highly colored.

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Explanation of the structure of the periodic table

The primary determinant of an element's chemical properties is its electron configuration, particularly of the outermost electrons (those in the valence shell). For instance, all atoms whose outermost shells are p-shells, and that have four electrons in that shell, will behave similarly, regardless of which p-shell it is. The shell in which the atom's outermost electron resides determines the block to which it belongs. The number of electrons within this shell determines the group within that block to which the belongs.

The total number of electron shells an atom has determines to which period it belongs. Each shell is divided into different subshells, which as atomic number increases are filled in roughly this order:

1s
2s           2p
3s           3p
4s        3d 4p
5s        4d 5p
6s     4f 5d 6p
7s     5f 6d 7p
8s  5g 6f 7d 8p
...

Hence the structure of the table. Since the outermost electrons determine chemical properties, those tend to be similar within groups.

Progressing through a group from lightest element to heaviest element, the outer-shell electrons (those most readily accessible for participation in chemical reactions) are all in the same type of orbital, with a similar shape, but with increasingly higher energy and average distance from the nucleus. For instance, the outer-shell (or "valence") electrons of the first group, headed by hydrogen all have one electron in an s orbital. In hydrogen, that s orbital is in the lowest possible energy state of any atom, the first-shell orbital (and represented by hydrogen's position in the first period of the table). In francium, the heaviest element of the group, the outer-shell electron is in the seventh-shell orbital, significantly further out on average from the nucleus than those electrons filling all the shells below it in energy. As another example, both carbon and lead have four electrons in their outer shell orbitals.

Because of the importance of the outermost shell, the different regions of the periodic table are sometimes referred to as periodic table blocks, named according to the sub-shell in which the "last" electron resides, e.g. the s-block, the p-block, the d-block, etc.

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History

Main article: History of the periodic table

The original table was created without a knowledge of the inner structure of atoms: if one orders the elements by atomic mass, and then plots certain other properties against atomic mass, one sees an undulation or periodicity to these properties as a function of atomic mass. The first to recognize these regularities was the German chemist Johann Wolfgang Döbereiner who, in 1829, noticed a number of triads of similar elements:

Some triads
Element	Atomic mass	Density
chlorine	35.5	0.00156 g/cm³
bromine	79.9	0.00312 g/cm³
iodine	126.9	0.00495 g/cm³

calcium	40.1	1.55 g/cm³
strontium	87.6	2.6 g/cm³
barium	137	3.5 g/cm³

This was followed by the English chemist John Alexander Reina Newlands, who in 1865 noticed that the elements of similar type recurred at intervals of eight, which he likened to the octaves of music, though his law of octaves was ridiculed by his contemporaries. Finally, in 1869, the German Julius Lothar Meyer and the Russian chemist Dmitri Ivanovich Mendeleev almost simultaneously developed the first periodic table, arranging the elements by mass. However, Mendeleev plotted a few elements out of strict mass sequence in order to make a better match to the properties of their neighbours in the table, corrected mistakes in the values of several atomic masses, and predicted the existence and properties of a few new elements in the empty cells of his table. Mendeleev was later vindicated by the discovery of the electronic structure of the elements in the late 19th and early 20th century.

In the 1940s Glenn T. Seaborg identified the transuranic lathanides and the actinides, which may be placed within the table, or below (as shown above).

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Further resources

[1] Scerri, E.R., references to several scholarly articles by this author.
Mazurs, E.G., "Graphical Representations of the Periodic System During One Hundred Years". University of Alabama Press, Alabama. 1974.
Bouma, J., "An Application-Oriented Periodic Table of the Elements". J. Chem. Ed., 66 741 (1989).

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External links

"Periodic table (professional edition)". WebElements.
The IUPAC periodic table
"Presentation forms of the periodic table". Western Oregon University.
"A Brief History of the Development of Periodic Table". Western Oregon University.
"Visual Periodic Table". ChemSoc.org.
Derived from Chemsoc, with links to other tables under each individual element.
Barbalace, Kenneth L., "Biochemical Periodic Tables". KLBProductions.com.
Barthelmy, David, "Periodic table" Mineralogy Database. (mineral emphasis)
Counterman, Craig, "Periodic Table of the Elements : For each of many properties a separate periodic table and a graph showing the relation with the atomic number". MIT Course 3.091.
Gray, Theodore, "Wooden Periodic Table Table" (with samples)
Holler, F. James, and John P. Selegue, "Periodic Table of Comic Books". Department of Chemistry, University of Kentucky. 1996-2002.
Heilman, Chris, "The Pictorial Periodic Table". (Includes alternate styles: Stowe, Benfey, Zmaczynski, Giguere, Tarantola, Filling, Mendeleev)
"Periodic table". Los Alamos National Laboratory's Chemistry Division.
"Periodic Table of the Fermi Surfaces of Elemental Solids". The Fermi Surface Database
"Interactive NMR Frequency Map". Texas A&M.
"Periodic Table Elements". Israel Science and Technology Directory. 1999-2004. (sorted by physical characteristics)
"Periodic table applet". Dartmouth College. (Java)
Eric Scerri many scholarly articles on the Periodic System by the philosopher-chemist who teaches in the chemistry department at UCLA.
"ScienceIsGolden" educational vehicles: a teacher in California has been driving around in vehicles signed by physicists & promoting an educational-form of the periodic table.
Periodensystem.com: periodic table with several transations, easy to use
Dayah, Michael, "Periodic Table". Large full-color scalable text-only rendering.

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Periodic table

Contents

Groups

Group numbers

Standard periodic table

Other methods for displaying the chemical elements

Periodicity of chemical properties

Explanation of the structure of the periodic table

History

Further resources

See also

External links

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