The periodic table of the chemical elements is a tabular method of displaying the chemical elements. A table is both a mode of Visual communication and a means of arranging Data. A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. Although precursors to this table exist, its invention is generally credited to Russian chemist Dmitri Mendeleev in 1869. Russia (Россия Rossiya) or the Russian Federation ( Rossiyskaya Federatsiya) is a transcontinental Country extending A chemist is a Scientist trained in the Science of Chemistry. Dmitri Ivanovich Mendeleev (sometimes spelled Mendeleyev; Дми́трий Ива́нович Менделе́ев) ( &ndash) was a Russian chemist and Mendeleev intended the table to illustrate recurring ("periodic") trends in the properties of the elements. The layout of the table has been refined and extended over time, as new elements have been discovered, and new theoretical models have been developed to explain chemical behavior. ^[1]

The periodic table is now ubiquitous within the academic discipline of chemistry, providing an extremely useful framework to classify, systematize and compare all the many different forms of chemical behavior. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties A chemical substance is a Material with a definite chemical composition. The table has also found wide application in physics, biology, engineering, and industry. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. Foundations of modern biology There are five unifying principles Engineering is the Discipline and Profession of applying technical and scientific Knowledge and For other uses of this term see Industry (disambiguation An industry (from Latin industrius, "diligent industrious" The current standard table contains 117 confirmed elements as of January 27, 2008 (elements 1-116 and element 118). Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Ununhexium (ˌjuːnənˈhɛksiəm or /ˌʌnənˈhɛksiəm/ is the temporary name of a synthetic Superheavy element in the Periodic table that has the temporary Ununoctium (ˌjuːnəˈnɒktiəm or /ˌʌnəˈnɒktiəm/ also known as eka-radon or element 118, is the temporary IUPAC name for

Contents 1 Methods for displaying the periodic table 1.1 Standard periodic table 1.2 Alternative versions (Layout/view of the table) 2 Arrangement 3 Periodicity of chemical properties 3.1 Groups and periods 3.1.1 Periodic trends of groups 3.1.2 Periodic trends of periods 3.2 Examples 3.2.1 Noble gases 3.2.2 Halogens 3.2.3 Transition metals 3.2.4 Lanthanides and actinides 4 Structure of the periodic table 5 History 6 See also 7 References 8 Further reading 9 External links

Methods for displaying the periodic table

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

This common arrangement of the periodic table separates the lanthanides and actinides from other elements. In Chemistry a group, also known as a family, is a vertical column in the Periodic table of the Chemical elements There are 18 groups in Trends The alkali metals show a number of trends when moving down the group - for instance decreasing electronegativity increasing reactivity and decreasing melting and boiling Biological occurrences Beryllium's low aqueous solubility means it is rarely available to biological systems it has no known role in living organisms and when encountered Occurrence Scandium yttrium and the Lanthanides (except promethium tend to occur together in the Earth's crust and are relatively abundant compared with most D-block Biological occurances The group 4 elements are not known to be involved in the biological chemistry of any living systems Biological occurrences Of the group 5 elements only vanadium has been identified as playing a role in the biological chemistry of living systems it is involved in some of the Biological occurrences Group 6 is notable in that it contains some of the only elements in periods 5 and 6 with a known role in the biological chemistry of living organisms molybdenum See also "Group 8" redirects here For the Swedish organization see Group 8 (Sweden. Applications Alloys with other metals primarially to add corrosion and wear resistance Industrial Catalysts Superalloys Electrical Properties Group ten metals are white to light grey in color and possess a high Luster, a resistance to tarnish( Oxidation) at STP, are highly See also See also History Carbon, Tin, and Lead, are a few of the elements well known in the ancient world - together with Sulfur, Iron, See also Gold chalcogenides Periodic table Abundance Owing to their high Reactivity, the halogens are found in the environment only in compounds or as Ions Halide ions and oxoanions History Noble gas is translated from the German noun de ''Edelgas'' first used in 1898 by Hugo Erdmann to indicate their extremely low level of reactivity In the Periodic table of the elements, a period is a horizontal row of the table A period 1 element is one of the Chemical elements in the first row (or period) of the periodic table of the chemical elements. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical A period 2 element is one of the Chemical elements in the second row (or period) of the periodic table of the chemical elements. Lithium (ˈlɪθiəm is a Chemical element with the symbol Li and Atomic number 3 Beryllium (bəˈrɪliəm is a Chemical element with the symbol Be and Atomic number 4 Boron (ˈbɔərɒn is a Chemical element with Atomic number 5 and the chemical symbol B. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Fluorine, fluorum meaning "to flow" is the Chemical element with the symbol F and Atomic number 9 Neon (ˈniːɒn is the Chemical element that has the symbol Ne and Atomic number 10 A period 3 element is one of the Chemical elements in the third row (or period) of the periodic table of the elements. Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 WikipediaNaming Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Phosphorus, (ˈfɒsfərəs is the Chemical element that has the symbol P and Atomic number 15 Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and This article pertains to the chemical element For other uses see Argon (disambiguation. A period 4 element is one of the Chemical elements in the fourth row (or period) of the periodic table of the elements. Potassium (pəˈtæsiəm is a Chemical element. It has the symbol K (kalium from qalīy Atomic number 19 and Atomic mass 39 Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 Scandium (ˈskændiəm is a Chemical element that has the symbol Sc and Atomic number 21 Titanium (taɪˈteɪniəm is a Chemical element with the symbol Ti and Atomic number 22 Vanadium (vəˈneɪdiəm is a Chemical element that has the symbol V and Atomic number 23 Chromium (ˈkroʊmiəm is a Chemical element which has the symbol Cr and Atomic number 24 Manganese (ˈmæŋgəniːz is a Chemical element, designated by the symbol Mn. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Cobalt (ˈkoʊbɒlt is a hard lustrous silver-grey Metal, a Chemical element with symbol Co. Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30 Gallium (ˈgæliəm is a Chemical element that has the symbol Ga and Atomic number 31 Germanium (dʒɚˈmeɪniəm is a Chemical element with the symbol Ge and Atomic number 32 Arsenic (ˈɑrsənɪk is a Chemical element that has the symbol As and Atomic number of 33 Selenium (səˈliniəm is a Chemical element with the Atomic number 34 represented by the chemical symbol Se, an atomic mass of 78 Krypton (ˈkrɪptən or /ˈkrɪptɒn/ from kryptos "hidden" is a Chemical element with the symbol Kr and Atomic number 36 A period 5 element is one of the Chemical elements in the fifth row (or period) of the periodic table of the elements. Rubidium (ruːˈbɪdiəm /rəˈbɪdiəm/ is a Chemical element with the symbol Rb and Atomic number 37 Strontium (ˈstrɒntiəm /ˈstrɒnʃiəm/) is a Chemical element with the symbol Sr and the Atomic number 38 Yttrium (ˈɪtriəm is a Chemical element with symbol Y and Atomic number 39 Zirconium (zɚˈkoʊniəm /ˌzɝˈkoʊniəm/ is a Chemical element with the symbol Zr and Atomic number 40 Niobium (naɪˈoʊbiəm or columbium (/kəˈlʌmbiəm/ is a Chemical element that has the symbol Nb and Atomic number 41 Molybdenum (məˈlɪbdənəm from the Greek word for the metal " Lead " is a Group 6 Chemical element with the symbol Mo Technetium (tɛkˈniːʃɪəm is the lightest Chemical element with no Stable isotope. Ruthenium (ruːˈθiːniəm is a Chemical element that has the symbol Ru and Atomic number 44 Rh redirects here For other uses see Rh (disambiguation Rhodium (ˈroʊdiəm is a Chemical element with the symbol Palladium (pronounced \pəˈleɪdiəm\ is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it palladium after the Silver (ˈsɪlvɚ is a Chemical element with the symbol " Ag " (argentum from the Ancient Greek: ἀργήντος - argēntos gen Cadmium (ˈkædmiəm is a Chemical element with the symbol Cd and Atomic number 48 Indium (ˈɪndiəm is a Chemical element with chemical symbol In and Atomic number 49 Tin is a Chemical element with the symbol Sn (stannum and Atomic number 50 Antimony (IPA (Received Pronunciation, /ˈæntɪmoʊni/ (US is a Chemical element with the symbol Sb (stibium meaning "mark" and Tellurium (tɪˈlʊəriəm/ /tɛl- is a Chemical element that has the symbol Te and Atomic number 52 Iodine (ˈaɪədaɪn ˈaɪədɪn or /ˈaɪədiːn/ from ιώδης iodes "violet" is a Chemical element that has the symbol I and Atomic Xenon (ˈzɛnɒn or) is a Chemical element represented by the symbol Xe. A period 6 element is one of the Chemical elements in the sixth row (or period) of the periodic table of the elements, including the Lanthanides Caesium or cesium (ˈsiːziəm is the Chemical element with the symbol Cs and Atomic number 55 Barium (ˈbɛəriəm is a Chemical element. It has the symbol Ba, and Atomic number 56 Terminology The Trivial name " Rare earths " is sometimes used to describe all the lanthanoids together with Scandium and Yttrium Hafnium (ˈhæfniəm is a Chemical element that has the symbol Hf and Atomic number 72 Tantalum (ˈtæntələm (formerly tantalium /tænˈtæliəm/ is a Chemical element with the symbol Ta and Atomic number 73 Tungsten (ˈtʌŋstən also known as wolfram (/ˈwʊlfrəm/ is a Chemical element that has the symbol W and Atomic number 74 Rhenium (ˈriːniəm is a Chemical element with the symbol Re and Atomic number 75 Osmium (ˈɒzmiəm is a Chemical element that has the symbol Os and Atomic number 76 Iridium (ɪˈrɪdiəm is a Chemical element that has the symbol Ir and Atomic number 77 Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 Gold (ˈɡoʊld is a Chemical element with the symbol Au (from its Latin name aurum) and Atomic number 79 Mercury (ˈmɜrkjʊri also called quicksilver or hydrargyrum, is a Chemical element with the symbol Hg ( Latinized hydrargyrum Thallium (ˈθæliəm is a Chemical element with the symbol Tl and Atomic number 81 Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly Bismuth (ˈbɪzməθ is a Chemical element that has the symbol Bi and Atomic number 83 Polonium (pəˈloʊniəm is a Chemical element with the symbol Po and Atomic number 84 discovered in 1898 by Marie and Pierre Curie Astatine (ˈæstətiːn is a Radioactive Chemical element with the symbol At and Atomic number 85 Radon (ˈreɪdɒn is the Chemical element that has the symbol Rn and Atomic number 86 A period 7 element is one of the Chemical elements in the seventh row (or period) of the periodic table of the elements. Francium (ˈfrænsiəm formerly known as eka-caesium and actinium K, is a Chemical element that has the symbol Fr and Radium (ˈreɪdiəm is a radioactive Chemical element which has the symbol Ra and Atomic number 88 History of the actinoid series From the earlier known chemical properties of actinium (89 up to uranium (92 indicating a relation to the Transition metals it was generally Rutherfordium (ˌrʌðɚˈfɔrdiəm is a Chemical element in the Periodic table that has the symbol Rf and Atomic number 104 Dubnium (ˈduːbniəm is a Chemical element in the Periodic table that has the symbol Db and Atomic number 105 Seaborgium (siːˈbɔrgiəm is a Chemical element in the Periodic table that has the symbol Sg and Atomic number 106 Image of Seaborgium Bohrium (ˈbɔəriəm is a Chemical element in the Periodic table that has the symbol Bh and Atomic number 107 Hassium (ˈhæsiəm or /ˈhɑːsiəm/ is a Synthetic element in the Periodic table that has the symbol Hs and Atomic number 108 Meitnerium (maɪtˈnɜriəm is a Chemical element in the Periodic table that has the symbol Mt and Atomic number 109 Darmstadtium (dɑrmˈʃtætiəm formerly known as Ununnilium is a Chemical element with the symbol Ds and Atomic number 110 Roentgenium (rɛntˈgɛniəm /rʌntˈdʒɛniəm/ is a Chemical element in the Periodic table that has the symbol Rg and Atomic number Ununtrium (juːˈnʌntriəm or /əˈnʌntriəm/ is the temporary name of a Synthetic element in the Periodic table that has the temporary symbol Uut and Ununquadium (ˌjuːnənˈkwɒdiəm or /ˌʌnənˈkwɒdiəm/ is the temporary name of a radioactive Chemical element in the Periodic table that has the Ununpentium (ˌjuːnənˈpɛntiəm or /ˌʌnənˈpɛntiəm/ is the temporary name of a synthetic Superheavy element in the Periodic table that has the Ununhexium (ˌjuːnənˈhɛksiəm or /ˌʌnənˈhɛksiəm/ is the temporary name of a synthetic Superheavy element in the Periodic table that has the temporary Ununseptium (ˌjuːnənˈsɛptiəm or /ˌʌnənˈsɛptiəm/ is the temporary name of an undiscovered Chemical element in the Periodic table that has the temporary Ununoctium (ˌjuːnəˈnɒktiəm or /ˌʌnəˈnɒktiəm/ also known as eka-radon or element 118, is the temporary IUPAC name for Terminology The Trivial name " Rare earths " is sometimes used to describe all the lanthanoids together with Scandium and Yttrium Lanthanum (ˈlænθənəm is a Chemical element with the symbol La and Atomic number 57 Cerium (ˈsɪəriəm is a Chemical element with the symbol Ce and Atomic number 58 Praseodymium (ˌpreɪzioʊˈdɪmiəm or /ˌpreɪsioʊˈdɪmiəm/ is a Chemical element that has the symbol Pr and Atomic number 59 Neodymium (ˌniːoʊˈdɪmiəm is a Chemical element with the symbol Nd and Atomic number 60 Promethium (prəˈmiːθiəm/ /proʊˈmiːθiəm is a Chemical element with the symbol Pm and Atomic number 61 Samarium (səˈmɛəriəm is a Chemical element with the symbol Sm and Atomic number 62 Europium (jʊˈroʊpiəm is a Chemical element with the symbol Eu and Atomic number 63 Gadolinium (ˌgædəˈlɪniəm is a Chemical element that has the symbol Gd and Atomic number 64 Terbium (ˈtɝbiəm is a Chemical element with the symbol Tb and Atomic number 65 Holmium (ˈhoʊlmiəm is a Chemical element with the symbol Ho and Atomic number 67 Erbium (ˈɝbiəm is a Chemical element with the symbol Er and Atomic number 68 Thulium (ˈθjuːliəm is a Chemical element that has the symbol Tm and Atomic number 69 Lutetium (ljuːˈtiːʃiəm is a Chemical element with the symbol Lu and Atomic number 71 History of the actinoid series From the earlier known chemical properties of actinium (89 up to uranium (92 indicating a relation to the Transition metals it was generally Actinium (ækˈtɪniəm is a radioactive Chemical element with the symbol Ac and Atomic number 89 which was discovered in 1899, the earliest Thorium (ˈθɔːriəm is a Chemical element with the symbol Th and Atomic number 90 Protactinium (ˌproʊtækˈtɪniəm is a Chemical element with the symbol Pa and Atomic number 91 Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the Neptunium (nɛpˈtjuːniəm is a Chemical element with the symbol Np and Atomic number 93 Americium (ˌæməˈrɪsiəm is a Synthetic element that has the symbol Am and Atomic number 95 This article is about the chemical element Curium for the ancient city also called Curium (located in Cyprus see Kourion Curium (ˈkjuːriəm Bk redirects here For other uses of the abbreviation see BK (disambiguation. Californium (ˌkælɪˈforniəm is a Metallic Chemical element with the symbol Cf and Atomic number 98 Einsteinium (aɪnˈstaɪniəm is a Metallic Synthetic element. Fermium (ˈfɝmiəm is a Synthetic element with the symbol Fm and Atomic number 100 Mendelevium (ˌmɛndəˈlɛviəm is a Synthetic element with the symbol Md (formerly Mv) and the Atomic number 101 Nobelium (noʊˈbɛliəm or /noʊˈbiːliəm/ is a Synthetic element with the symbol No and Atomic number 102 Lawrencium (ləˈrɛnsiəm is a Radioactive Synthetic element with the symbol Lr (formerly Lw) and Atomic number 103 The Wide Periodic Table incorporates the f-block. This is a version of the periodic table of the elements that places all elements of one period in the same row The f-block of the Periodic table of the elements consists of those elements (sometimes referred to as the inner transition elements) for which in the The Extended Periodic Table adds the 8th and 9th periods, incorporating the f-block and adding the theoretical g-block. The g-block is a hypothetical region in the Periodic table of the elements.

Element categories in the periodic table Metals Metalloids Nonmetals Unknown Alkali metals Alkaline earth metals Inner transition elements Transition elements Other metals Other nonmetals Halogens Noble gases Lanthanides Actinides
Atomic number colors show state at standard temperature and pressure (0 °C and 1 atm) Solids Liquids Gases Unknown	Borders show natural occurrence Primordial From decay Synthetic Undiscovered

Alternative versions (Layout/view of the table)

• The wide table sets inline the f-block of lanthanides and actinides. Collective names of groups of like elements is the term used by IUPAC to describe nomenclature for Categorization of Chemical elements The The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across Metalloid is a term used in Chemistry when classifying the Chemical elements On the basis of their general physical and chemical properties nearly every element Nonmetal is a term used in Chemistry when classifying the Chemical elements On the basis of their general physical and chemical properties every element in the Trends The alkali metals show a number of trends when moving down the group - for instance decreasing electronegativity increasing reactivity and decreasing melting and boiling Biological occurrences Beryllium's low aqueous solubility means it is rarely available to biological systems it has no known role in living organisms and when encountered The f-block of the Periodic table of the elements consists of those elements (sometimes referred to as the inner transition elements) for which in the In Chemistry, the term transition metal (sometimes also called a transition element) has two possible meanings It commonly refers to any element in The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across Nonmetal is a term used in Chemistry when classifying the Chemical elements On the basis of their general physical and chemical properties every element in the Abundance Owing to their high Reactivity, the halogens are found in the environment only in compounds or as Ions Halide ions and oxoanions History Noble gas is translated from the German noun de ''Edelgas'' first used in 1898 by Hugo Erdmann to indicate their extremely low level of reactivity Terminology The Trivial name " Rare earths " is sometimes used to describe all the lanthanoids together with Scandium and Yttrium History of the actinoid series From the earlier known chemical properties of actinium (89 up to uranium (92 indicating a relation to the Transition metals it was generally See also List of elements by atomic number In Chemistry and Physics, the atomic number (also known as the proton A state of matter (or physical state, or form of matter) has physical properties which are qualitatively different from other states of matter In Physical sciences standard conditions for temperature and pressure are Standard sets of conditions for experimental measurements to allow comparisons to be made A trace radioisotope is a Radioisotope that occurs naturally in trace amounts (i In chemistry the Chemical elements labeled as synthetic are too unstable to be found naturally on Earth. This is a version of the periodic table of the elements that places all elements of one period in the same row Terminology The Trivial name " Rare earths " is sometimes used to describe all the lanthanoids together with Scandium and Yttrium History of the actinoid series From the earlier known chemical properties of actinium (89 up to uranium (92 indicating a relation to the Transition metals it was generally
• The standard table (same as above) provides the basics. This is a typical display of the periodic table of the elements and contains the symbol and Atomic number of each element
• A vertical table scrolls down for narrow pages. The alternative periodic table is a standard Periodic table rotated counterclockwise and then mirrored across the vertical axis so that the lower groups are to the left and
• The big table provides the basics and full element names.
• The large table provides the above and atomic masses. This is a large version of the periodic table and contains the symbol atomic number and mean Atomic mass value for the natural isotopic composition of each element The atomic mass (ma is the Mass of an atom most often expressed in unified atomic mass units The atomic mass may be considered to be the total mass
• The detailed table provides a smaller version of the huge table.
• The Electronegativity table provides electronegativities. " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons
• Electron configurations
• Metals and non-metals
• The blocks are shaded instead of series. Helium is placed next to Hydrogen instead of on top of Neon because it is part of the s2 group
• The valences are shaded instead of series.

Other alternative periodic tables exist. Alternative periodic tables are Chemical element displays different from the well known Mendeleev periodic table.

Some versions of the table show a dark stair-step line along the metalloids. Metals are to the left of the line and non-metals to the right. ^[2]

Arrangement

The layout of the periodic table demonstrates recurring ("periodic") chemical properties. Elements are listed in order of increasing atomic number (i. See also List of elements by atomic number In Chemistry and Physics, the atomic number (also known as the proton e. the number of protons in the atomic nucleus). The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom Rows are arranged so that elements with similar properties fall into the same vertical columns ("groups"). According to quantum mechanical theories of electron configuration within atoms, each horizontal row ("period") in the table corresponded to the filling of a quantum shell of electrons. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J There are progressively longer periods further down the table, grouping the elements into s-, p-, d- and f-blocks to reflect their electron configuration.

In printed tables, each element is usually listed with its element symbol and atomic number; many versions of the table also list the element's atomic mass and other information, such as its abbreviated electron configuration, electronegativity and most common valence numbers. See also Chemical formula. A chemical symbol is an Abbreviation or shortened version of the name of a Chemical element See also List of elements by atomic number In Chemistry and Physics, the atomic number (also known as the proton The atomic mass (ma is the Mass of an atom most often expressed in unified atomic mass units The atomic mass may be considered to be the total mass In Atomic physics and Quantum chemistry, electron configuration is the arrangement of Electrons in an Atom, Molecule, or other " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons In Chemistry, valence, also known as valency or valency number, is a measure of the number of Chemical bonds formed by the Atoms

As of 2006, the table contains 117 chemical elements whose discoveries have been confirmed. Ninety-four are found naturally on Earth, and the rest are synthetic elements that have been produced artificially in particle accelerators. In chemistry the Chemical elements labeled as synthetic are too unstable to be found naturally on Earth. Elements 43 (technetium), 61 (promethium), 93 (neptunium) and 94 (plutonium) have no stable isotopes and were first discovered synthetically; however, they were later discovered in trace amounts on earth as products of natural radioactive decay processes.

Periodicity of chemical properties

The main value of the periodic table is the ability to predict the chemical properties of an element based on its location on the table. It should be noted that the properties vary differently when moving vertically along the columns of the table, than when moving horizontally along the rows.

Groups and periods

• A group is a vertical column in the periodic table of the elements. In Chemistry a group, also known as a family, is a vertical column in the Periodic table of the Chemical elements There are 18 groups in

Groups are considered the most important method of classifying the elements. In some groups, the elements have very similar properties and exhibit a clear trend in properties down the group — these groups tend to be given trivial (unsystematic) names, e. g. the alkali metals, alkaline earth metals, halogens and noble gases. Trends The alkali metals show a number of trends when moving down the group - for instance decreasing electronegativity increasing reactivity and decreasing melting and boiling Biological occurrences Beryllium's low aqueous solubility means it is rarely available to biological systems it has no known role in living organisms and when encountered Abundance Owing to their high Reactivity, the halogens are found in the environment only in compounds or as Ions Halide ions and oxoanions History Noble gas is translated from the German noun de ''Edelgas'' first used in 1898 by Hugo Erdmann to indicate their extremely low level of reactivity Some other groups in the periodic table display fewer similarities and/or vertical trends (for example Groups 14 and 15), and these have no trivial names and are referred to simply by their group numbers.

• A period is a horizontal row in the periodic table of the elements. In the Periodic table of the elements, a period is a horizontal row of the table

Although groups are the most common way of classifying elements, there are some regions of the periodic table where the horizontal trends and similarities in properties are more significant than vertical group trends. This can be true in the d-block (or "transition metals"), and especially for the f-block, where the lanthanides and actinides form two substantial horizontal series of elements. The d-block of the periodic table of the elements consists of those Periodic table groups that contain elements in which in the atomic ground state the highest-energy In Chemistry, the term transition metal (sometimes also called a transition element) has two possible meanings It commonly refers to any element in The f-block of the Periodic table of the elements consists of those elements (sometimes referred to as the inner transition elements) for which in the Terminology The Trivial name " Rare earths " is sometimes used to describe all the lanthanoids together with Scandium and Yttrium History of the actinoid series From the earlier known chemical properties of actinium (89 up to uranium (92 indicating a relation to the Transition metals it was generally

Periodic trends of groups

Modern quantum mechanical theories of atomic structure explain group trends by proposing that elements within the same group have the same electron configurations in their valence shell, which is the most important factor in accounting for their similar properties. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons An electron shell may be crudely thought of as an Orbit followed by Electrons around an Atom nucleus. Elements in the same group also show patterns in their atomic radius, ionization energy, and electronegativity. Atomic radius, and more generally the size of an atom, is not a precisely defined Physical quantity, nor is it constant in all circumstances The ionization potential, ionization energy or EI of an Atom or Molecule is the Energy required to remove an Electron " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons From top to bottom in a group, the atomic radii of the elements increase. Since there are more filled energy levels, electrons are found farther from the nucleus. From the top, each successive element has a lower ionization energy because it is easier to remove an electron since the atoms are less tightly bound. Similarly, a group will also see a top to bottom decrease in electronegativity due to an increasing distance between valence electrons and the nucleus.

Periodic trends of periods

Elements in the same period show trends in atomic radius, ionization energy, electron affinity, and electronegativity. Atomic radius, and more generally the size of an atom, is not a precisely defined Physical quantity, nor is it constant in all circumstances The ionization potential, ionization energy or EI of an Atom or Molecule is the Energy required to remove an Electron The electron affinity, E ea of an Atom or Molecule is the energy required to detach an electron from a singly charged negative " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons Moving left to right across a period, atomic radius usually decreases. This occurs because each successive element has an added proton and electron which causes the electron to be drawn closer to the nucleus. This decrease in atomic radius also causes the ionization energy to increase when moving from left to right across a period. The more tightly bound an element is, the more energy is required to remove an electron. Similarly, electronegativity will increase in the same manner as ionization energy because of the amount of pull that is exerted on the electrons by the nucleus. Electron affinity also shows a slight trend across a period. The electron affinity, E ea of an Atom or Molecule is the energy required to detach an electron from a singly charged negative Metals (left side of a period) generally have a lower electron affinity than nonmetals (right side of a period) with the exception of the noble gases.

Examples

Noble gases

All the elements of Group 18, the noble gases, have full valence shells. History Noble gas is translated from the German noun de ''Edelgas'' first used in 1898 by Hugo Erdmann to indicate their extremely low level of reactivity This means they do not need to react with other elements to attain a full shell, and are therefore much less reactive than other groups. Helium and neon are the most inert elements among noble gases, since reactivity, in this group, increases with the periods: it is possible to make heavy noble gases react since they have much larger electron shells. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Neon (ˈniːɒn is the Chemical element that has the symbol Ne and Atomic number 10 In English to be inert is to be in a state of doing little or nothing However, their reactivity remains very low in absolute terms.

Halogens

In Group 17, known as the halogens, elements are missing just one electron each to fill their shells. Abundance Owing to their high Reactivity, the halogens are found in the environment only in compounds or as Ions Halide ions and oxoanions Therefore, in chemical reactions they tend to acquire electrons (the tendency to acquire electrons is called electronegativity). " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons This property is most evident for fluorine (the most electronegative element of the whole table), and it diminishes with increasing period. Fluorine, fluorum meaning "to flow" is the Chemical element with the symbol F and Atomic number 9

As a result, all halogens form acids with hydrogen, such as hydrofluoric acid, hydrochloric acid, hydrobromic acid and hydroiodic acid, all in the form HX. Hydrofluoric acid is a Solution of Hydrogen fluoride in Water. Hydrochloric acid is the Solution of Hydrogen chloride ( H[[Chlorine Cl]] in water Hydrobromic Acid is formed by dissolving the diatomic molecule Hydrogen bromide in water Hydrogen iodide (HI is a Diatomic molecule. Aqueous solutions of HI are known as hydroiodic acid or hydriodic acid, a Strong acid. Their acidity increases with higher period, for example, with regard to iodine and fluorine, since a large I⁻ ion is more stable in solution than a small F⁻, there is less volume in which to disperse the charge. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge

Transition metals

For the transition metals (Groups 3 to 12), horizontal trends across periods are often important as well as vertical trends down groups; the differences between groups adjacent are usually not dramatic. In Chemistry, the term transition metal (sometimes also called a transition element) has two possible meanings It commonly refers to any element in Transition metal reactions often involve coordinated species.

Lanthanides and actinides

The chemical properties of the lanthanides (elements 57–71) and the actinides (elements 89–103) are even more similar to each other than the transition metals, and separating a mixture of these can be very difficult. Terminology The Trivial name " Rare earths " is sometimes used to describe all the lanthanoids together with Scandium and Yttrium History of the actinoid series From the earlier known chemical properties of actinium (89 up to uranium (92 indicating a relation to the Transition metals it was generally In Chemistry, the term transition metal (sometimes also called a transition element) has two possible meanings It commonly refers to any element in This is important in the chemical purification of uranium concerning nuclear power. Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the Nuclear power is any Nuclear technology designed to extract usable Energy from atomic nuclei via controlled Nuclear reactions

Structure of the periodic table

The primary determinant of an element's chemical properties is its electron configuration, particularly the valence shell electrons. In Atomic physics and Quantum chemistry, electron configuration is the arrangement of Electrons in an Atom, Molecule, or other An electron shell may be crudely thought of as an Orbit followed by Electrons around an Atom nucleus. For instance, any atoms with four valence electrons occupying p orbitals will exhibit some similarity. The type of orbital in which the atom's outermost electrons reside determines the "block" to which it belongs. The number of valence shell electrons determines the family, or group, to which the element belongs. An electron shell may be crudely thought of as an Orbit followed by Electrons around an Atom nucleus.

The total number of electron shells an atom has determines the period to which it belongs. An electron shell may be crudely thought of as an Orbit followed by Electrons around an Atom nucleus. Each shell is divided into different subshells, which as atomic number increases are filled in roughly this order (the Aufbau principle):

Subshell:	S	G	F	D	P
Period
1	1s
2	2s				2p
3	3s				3p
4	4s			3d	4p
5	5s			4d	5p
6	6s		4f	5d	6p
7	7s		5f	6d	7p
8	8s	5g	6f	7d	8p

Hence the structure of the table. The Aufbau principle (from the German Aufbau meaning "building up construction" also Aufbau rule or building-up principle) is 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. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 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. Francium (ˈfrænsiəm formerly known as eka-caesium and actinium K, is a Chemical element that has the symbol Fr and As another example, both carbon and lead have four electrons in their outer shell orbitals.

Note that as atomic number (i. See also List of elements by atomic number In Chemistry and Physics, the atomic number (also known as the proton e. charge on the atomic nucleus) increases, this leads to greater spin-orbit coupling between the nucleus and the electrons, reducing the validity of the quantum mechanical orbital approximation model, which considers each atomic orbital as a separate entity. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom In Quantum physics, the spin-orbit interaction (also called spin-orbit effect or spin-orbit coupling) is any interaction of a particle's spin

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. A block of the Periodic table of elements is a set of adjacent groups The respective highest-energy electrons in each element in a block belong to the same Atomic g. the s-block, the p-block, the d-block, etc.

Regarding the elements Ununbium, ununtrium, ununquadium, etc. , they are elements that have been discovered, but so far have not been named.

History

Main article: History of the periodic table

In Ancient Greece, the influential Greek philosopher Aristotle proposed that there were four main elements: air, fire, earth and water. The Periodic table is a tabular method of displaying the chemical elements Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a Greek philosopher a student of Plato and teacher of Alexander the Great. All of these elements could be reacted to create another one; e. g. , earth and fire combined to form lava. However, this theory was dismissed when the real chemical elements started being discovered. Scientists needed an easily accessible, well organized database with which information about the elements could be recorded and accessed. This was to be known as the periodic table.

The original table was created before the discovery of subatomic particles or the formulation of current quantum mechanical theories of atomic structure. A subatomic particle is an elementary or composite Particle smaller than an Atom. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny 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 atomic mass (ma is the Mass of an atom most often expressed in unified atomic mass units The atomic mass may be considered to be the total 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)
chlorine	35. Johann Wolfgang Döbereiner ( December 13, 1780 &ndash March 24, 1849) was a German chemist who is best known for 453	0. 0032
bromine	79. 904	3. 1028
iodine	126. 90447	4. 933
calcium	40. 078	1. 55
strontium	87. 62	2. 54
barium	137. 327	3. 594

In 1829 Döbereiner proposed the Law of Triads: The middle element in the triad had atomic weight that was the average of the other two members. The densities of some triads followed a similar pattern. Soon other scientists found chemical relationships extended beyond triads. Fluorine was added to Cl/Br/I group; sulfur, oxygen, selenium and tellurium were grouped into a family; nitrogen, phosphorus, arsenic, antimony, and bismuth were classified as another group.

This was followed by the English chemist John Newlands, who noticed in 1865 that when placed in order of increasing atomic weight, elements of similar physical and chemical properties recurred at intervals of eight, which he likened to the octaves of music, though his law of octaves was ridiculed by his contemporaries. John Alexander Reina Newlands (November 1837 – July 29, 1898) was an English analytical chemist who prepared in 1863 the first In Music, an octave ( is the the use of which is "common in most musical systems ^[3] However, while successful for some elements, Newlands' law of octaves failed for two reasons:

1. It was not valid for elements that had atomic masses higher than Ca.
2. When further elements were discovered, such as the noble gases (He, Ne, Ar), they could not be accommodated in his table.

Finally, in 1869 the Russian chemistry professor Dmitri Ivanovich Mendeleev and four months later the German Julius Lothar Meyer independently developed the first periodic table, arranging the elements by mass. Dmitri Ivanovich Mendeleev (sometimes spelled Mendeleyev; Дми́трий Ива́нович Менделе́ев) ( &ndash) was a Russian chemist and Julius Lothar Meyer ( August 19, 1830 - April 11, 1895) was born in Varel, at that time belonging to the duchy of Oldenburg However, Mendeleev plotted a few elements out of strict mass sequence in order to make a better match to the properties of their neighbors 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.

Earlier attempts to list the elements to show the relationships between them (for example by Newlands) had usually involved putting them in order of atomic mass. John Alexander Reina Newlands (November 1837 – July 29, 1898) was an English analytical chemist who prepared in 1863 the first The atomic mass (ma is the Mass of an atom most often expressed in unified atomic mass units The atomic mass may be considered to be the total mass Mendeleev's key insight in devising the periodic table was to lay out the elements to illustrate recurring ("periodic") chemical properties (even if this meant some of them were not in mass order), and to leave gaps for "missing" elements. Mendeleev used his table to predict the properties of these "missing elements", and many of them were indeed discovered and fit the predictions well.

With the development of theories of atomic structure (for instance by Henry Moseley) it became apparent that Mendeleev had listed the elements in order of increasing atomic number (i. History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny Henry Gwyn Jeffreys Moseley ( November 23, 1887 – August 10, 1915) was an English physicist. See also List of elements by atomic number In Chemistry and Physics, the atomic number (also known as the proton e. the net amount of positive charge on the atomic nucleus). The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom This sequence is nearly identical to that resulting from ascending atomic mass.

In order to illustrate recurring properties, Mendeleev began new rows in his table so that elements with similar properties fell into the same vertical columns ("groups").

With the development of modern quantum mechanical theories of electron configuration within atoms, it became apparent that each horizontal row ("period") in the table corresponded to the filling of a quantum shell of electrons. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J In Mendeleev's original table, each period was the same length. Modern tables have progressively longer periods further down the table, and group the elements into s-, p-, d- and f-blocks to reflect our understanding of their electron configuration.

In the 1940s Glenn T. Seaborg identified the transuranic lanthanides and the actinides, which may be placed within the table, or below (as shown above). Glenn Theodore Seaborg ( Glenn Teodor Sjöberg) ( April 19, 1912 &ndash February 25, 1999) won the 1951 Nobel Prize in Chemistry In Chemistry, transuranium elements (also known as transuranic elements) are the Chemical elements with Atomic numbers greater than 92 (the atomic

See also

References

• Theodore L. Brown, H. Eugene LeMay, and Bruce E. Bursten (2005). Chemistry:The Central Science, 10th edition, Prentice Hall. ISBN 0-13-109686-9.  
• Helmenstine, Marie (2007). Trends in the Periodic Table. About, Inc. . Retrieved on 2007-01-27. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 98 - Trajan becomes Roman Emperor after the death of Nerva.

Further reading

• 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).
• Eric R. Scerri, The Periodic Table: Its Story and Its Significance, Oxford University Press, 2006.
• Imyanitov, N. S. , "Mathematical description of dialectic regular trends in the periodic system", Russ. J. Gen. Chem. , 69, 509 (1999) [Eng].
• Imyanitov, N. S. , "Modification of Various Functions for Description of Periodic Dependences", Russ. J. Coord. Chem. , 29, 46 (2003) [Eng].

External links

• WebElements comprehensive periodic table
• Ptable.com JavaScript periodic table
• Time of discovery IUPAC periodic table
• Visual Elements. ChemSoc. org.
• Los Alamos National Laboratory's chemistry division presents Periodic Table of the Elements—Online version, PDF version
• Gray, Theodore, The Wooden Periodic Table Table: actual table containing samples of each naturally occurring element.
• Videos about elements in the periodic table
• Mnemonic methods for learning the periodic table
• Syncopated Systems detailed rotated periodic table
• Chemogenesis Periodic Table Formulations

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