Periodic table

Next (Periodic table, main group elements)

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 configuration so that many chemical properties follow a regular pattern across the table. Each element is listed by its atomic number and chemical symbol. Mendeleev's ordering of the periodic table was one of the greatest developments in modern chemistry. Chemists were able to quantitatively explain the behavior of the elements, and to predict the existence of yet undiscovered ones. There are 116 chemical elements whose discoveries have been confirmed. Ninety-four can be found naturally on Earth, and the rest have been produced in laboratories.

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

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. They can also be called families.

Group numbers

There are three systems of group numbers; one using Arabic numerals (1, 2, ... 18), another using Roman numerals (I, II, ... VIII), and one using a combination of Roman numerals and Latin letters (IA, IIA, IB, ... VIIIA). 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.

Standard periodic table

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	*	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	**	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 metals	Alkaline earth metals	Lanthanides	Actinides	Transition metals
Poor metals	Metalloids	Nonmetals	Halogens	Noble gases

State at standard temperature and pressure

Elements numbered in red are gases.
Elements numbered in green are liquids.
Elements numbered in black are solids.

Natural occurrence

Elements without borders have not been discovered/synthesized yet.
Elements with dotted borders do not occur naturally (synthetic elements).
Elements with dashed borders naturally arise from decay of other chemical elements.
Elements with solid borders are older than the Earth (primordial elements).
- Note: Although californium (Cf, 98) is not Earth-primordial, it (and its decay products) does occur naturally: its electromagnetic emissions are regularly observed in supernova spectra.

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.

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, or energy level, 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 (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, while carbon is a solid which can be burned. Diamonds which are a form of crystallized carbon can also burn.

In the group known as the halogens, the element chlorine (Cl) falls between fluorine (F) and bromine (Br). Despite their dramatic differences in mass, their allotropes have very similar properties. They are all highly corrosive. Chlorine and fluorine are gases, while bromine is a very low-boiling liquid. Chlorine and bromine are brightly colored, whereas flourine is not.

Explanation of the structure of the periodic table

The primary determinant of an element's chemical properties is its electron configuration, particularly the valence shell electrons. For instance, all atoms whose four valence electrons are found on the p shell will behave similarly, regardless of which energy level that last p shell is on. The shell in which the atom's outermost electrons reside determines the "block" to which it belongs. The number of valence shell electrons determines which family, or group, the element belongs.

The total number of electron shells an atom has determines the period to which 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      5d      6p
7s      6d      7p
      4f
      5f
...

Hence the structure of the table. Since the outermost electrons determine chemical properties, those with the same number of valence electrons are grouped together..

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.

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	Molar mass (g/mol)	Density (g/cm³)	Quotient (cm³/mol)
chlorine	35.4527	0.003214	11030
bromine	79.904	3.122	25.6
iodine	126.90447	4.93	25.7

calcium	40.078	1.54	26.0
strontium	87.62	2.64	33.2
barium	137.327	3.594	38.2

This was followed by the English chemist John 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).

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).

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.

Periodic tables

Groups: 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18

Periods: 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8

Series: Alkalis - Alkaline earths - Lanthanides - Actinides - Transition metals - Poor metals - Metalloids - Nonmetals - Halogens - Noble gases

Blocks: s-block - p-block - d-block - f-block - g-block

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