History+of+the+period+table

History of the periodic table
Long long age, people did not know our world is made from different elements, when they saw something they cannot explain and how does it happened, they thought it is miracle and fear of it. Time goes by, when human's society developed, people found that our world is made by different kinds of elements, and they try to arrange the and study of it. “The **periodic table of the chemical elements** is a tabular (arranged in the form of a table) display of the chemical elements. Although precursors(existed before) to this table exist, its invention is generally credited to Russian chemist [|Dmitri Mendeleev] in 1869, who 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 of the many different forms of chemical behavior. The table has found wide application in chemistry, [|physics], [|biology], and [|engineering], especially [|chemical engineering]. The current standard table contains 118 elements as of March 2010 (elements [|1]–[|118]).” *（[] ） A modern periodic table. *（[] ）

Elemental ideas from ancient times
== *([]) == Long time ago, people only known some elements that is useful and expensive, like gold, silver and copper. Those elements all can discover in nature in native form and are relatively simple to mine with tools. However, the idea that were very limited. About 330 B.C Aristotle proposed that everything is made up of a mixture of one or more of four "roots", but later renamed elements by Plato. The four elements were earth, water, air and fire. They thought these were the principal elements that made our world. Howver, even thought this was a good notion, Aristotle's and Plato's ideas did nothing to advance the understanding of the nature of matter.

Age of Enlightenment
[|Hennig Brand] was the first person recorded to have discovered a new element. Brand was a poor German merchant who was trying to discover the [|Philosopher's Stone] — a mythical object that was supposed to turn inexpensive base [|metals] into gold. He experimented with distilling human urine until in 1649[|[3]] he finally obtained a glowing white substance which he named [|phosphorus]. He kept his discovery secret, until 1680 when [|Robert Boyle] rediscovered it and it became public. This and related discoveries raised the question of what it means for a substance to be an "element". In 1661 Boyle defined an element as a substance that cannot be broken down into a simpler substance by a chemical reaction. This simple definition actually served for nearly 300 years (until the development of the notion of subatomic particles), and even today is taught in introductory chemistry classes.
 * （[]）

Antoine-Laurent de Lavoisier
(*__http://www.google.com.hk/imgres?imgurl=http:www.lessignets.com/signetsdiane/calendrier/images/aout/26/lavoisier8888.jpg&imgrefurl=http://www.lessignets.com/signetsdiane/calendrier/aout/26.htm&usg=uv6P5hy_eu8Vmq-3q2ALJv_TuUo=&h=299&w=283&sz=17&hl=zh-TW&start=3&um=1&itbs=1&tbnid=ElOvtP0zKoxrWM:&tbnh=116&tbnw=110&prev=/images%3Fq%3DAntoine-Laurent%2Bde%2BLavoisier%26um%3D1%26hl%3Dzh-TW%26newwindow%3D1%26sa%3DN%26tbs%3Disch:1//__) [|Lavoisier]'s [|//Traité Élémentaire de Chimie//] (Elementary Treatise of Chemistry//, 1789, translated into English by [|Robert Kerr]) is considered to be the first modern chemical [|textbook]. It contained a list of elements, or substances that could not be broken down further, which included [|oxygen], [|nitrogen], [|hydrogen], [|phosphorus], [|mercury], [|zinc], and [|sulfur]. It also forms the basis for the modern list of elements. His list, however, also included [|light] and [|caloric], which he believed to be material substances. While many leading chemists of the time refused to believe Lavoisier's new revelations, the// Elementary Treatise //was written well enough to convince the younger generation. However, as Lavoisier's descriptions only classified elements as metals or non-metals, it fell short of a complete analysis.//

__Johann Wolfgang Döbereiner__

In 1817, //[|//Johann Wolfgang Döbereiner//]// began to formulate one of the earliest attempts to classify the elements. He found that some elements formed groups of three with related properties. He termed these groups "triads". Some triads classified by Döbereiner are: __,__ //[|//bromine//]//__, and__ > In all of the triads, the atomic weight of the second element was almost exactly the average of the atomic weights of the first and third element. [4] >
 * 1) [|//chlorine//]
 * //[|//iodine//]//
 * [|//calcium//]__,__ //[|//strontium//]//__, and__
 * //[|//barium//]//
 * [|//sulfur//]__,__ //[|//selenium//]//__, and__
 * //[|//tellurium//]//
 * [|//lithium//]__,__ //[|//sodium//]//__, and__
 * 1) //[|//potassium//]//

__Classifying Elements__

> By 1869//[|//[3//]//], a total of 63//[|//[3//]//] elements had been discovered. As the number of known elements grew, scientists began to recognize patterns in the way chemicals reacted and began to devise ways to classify the elements__.__ > > //__**Now the period table got more and more completed. After tere are manypeople who discovered other elements**.__

__Alexandre-Emile Béguyer de Chancourtois__
[|Alexandre-Emile Béguyer de Chancourtois], a French geologist, was the first person to notice the periodicity of the elements — similar elements seem to occur at regular intervals when they are ordered by their atomic weights. He devised an early form of periodic table, which he called the **telluric helix**. With the elements arranged in a spiral on a cylinder by order of increasing atomic weight, de Chancourtois saw that elements with similar properties lined up vertically. His chart included some ions and compounds in addition to elements. His paper was published in 1862, but used geological rather than chemical terms and did not include a diagram; as a result, it received little attention until the work of [|Dmitri Mendeleev].[|[5]] > John Newlands > > **John Newlands** > [|John Newlands] was an English chemist who in 1865 classified[|[6]] the 56 elements that had been discovered at the time into 11 groups which were based on similar physical properties. > Newlands noted that many pairs of similar elements existed which differed by some multiple of eight in atomic weight. However, his law of octaves//, likening this periodicity of eights to the musical scale, was ridiculed by his contemporaries. It was not until the following century, with [|Gilbert N. Lewis]' [|valence bond theory] (1916) and [|Irving Langmuir]'s octet theory of chemical bonding[|[7]][|[8]] (1919) that the importance of the periodicity of eight would be accepted > > **Mendeleev** > [|Dmitri Mendeleev], a [|Siberian]-born Russian chemist, was the first scientist to make a [|periodic table] much like the one we use today. Mendeleev arranged the elements in a table ordered by [|atomic weight], corresponding to relative [|molar mass] as defined today. It is sometimes said that he played "chemical solitaire" on long train rides using cards with various facts of known elements.[|[9]] On March 6, 1869, a formal presentation was made to the Russian Chemical Society, entitled //The Dependence Between the Properties of the Atomic Weights of the Elements//. His table was published in an obscure Russian journal but quickly republished in a German journal, //Zeitschrift für Chemie// (Eng., "Chemistry Magazine"), in 1869. It stated: > > // This version of [|Mendeleev]'s periodic table from 1891. It is lacking the [|noble gases] > **__Scientific benefits of Mendeleev's table__** __**Shortcomings of Mendeleev's table**__ > __ **Lothar Meyer** __ > Unknown to Mendeleev, [|Lothar Meyer] was also working on a periodic table. Although his work was published in 1864, and was done independently of Mendeleev, few historians regard him as an equal co-creator of the periodic table. For one thing, Meyer's table only included 28 elements. Furthermore, Meyer classified elements not by [|atomic weight], but by [|valence] alone. Finally, Meyer never came to the idea of predicting new elements and correcting atomic weights. Only a few months after Mendeleev published his periodic table of all known elements (and predicted several new elements to complete the table, plus some corrected atomic weights), Meyer published a virtually identical table. While a few people consider Meyer and Mendeleev the co-creators of the periodic table, most agree that, by itself, Mendeleev's accurate prediction of the qualities of the undiscovered elements lands him the larger share of credit. In any case, at the time Mendeleev's predictions greatly impressed his contemporaries and were eventually found to be correct. An English chemist, [|William Odling], also drew up a table that is remarkably similar to that of Mendeleev, in 1864__.__ > > **Refinements to the periodic table**__//
 * 1) The [|elements], if arranged according to their [|atomic weights], exhibit an apparent periodicity of properties.
 * 2) Elements which are similar as regards to their chemical properties have atomic weights which are either of nearly the same value (e.g., Pt, Ir, Os) or which increase regularly (e.g., K, Rb, Cs).
 * 3) The arrangement of the elements, or of groups of elements in the order of their atomic weights, corresponds to their so-called valencies, as well as, to some extent, to their distinctive chemical properties; as is apparent among other series in that of Li, Be, Ba, C, N, O, and Sn.
 * 4) The elements which are the most widely diffused have small atomic weights.
 * 5) The magnitude of the atomic weight determines the character of the element, just as the magnitude of the molecule determines the character of a compound body.
 * 6) We must expect the discovery of many yet unknown elements–for example, elements analogous to [|aluminium] and [|silicon]–whose atomic weight would be between 65 and 75.
 * 7) The atomic weight of an element may sometimes be amended by a knowledge of those of its contiguous elements. Thus the atomic weight of [|tellurium] must lie between 123 and 126, and cannot be 128. (This was based on the position of tellurium between [|antimony] and [|iodine] whose atomic weight is 127. However Moseley later explained the position of these elements without revising the atomic weight values — see below.)
 * 8) Certain characteristic properties of elements can be foretold from their atomic weights.
 * [|Mendeleev predicted the discovery of other elements] and left space for these new elements, namely eka-silicon ([|germanium]), eka-aluminium ([|gallium]), and eka-boron ([|scandium]). Thus, there was no disturbance in the periodic table.
 * He pointed out that some of the then current atomic weights were incorrect.
 * He provided for variance from atomic weight order.
 * His table did not include any of the [|noble gases], which were discovered later. These were added by Sir [|William Ramsay] as Group 0, without any disturbance to the basic concept of the periodic table.
 * There was no place for the [|isotopes] of the various elements, which were discovered later.

[[|edit]] Henry Moseley
In 1914 [|Henry Moseley] found a relationship between an element's [|X-ray] wavelength and its [|atomic number] (Z), and therefore resequenced the table by nuclear charge rather than atomic weight. Before this discovery, atomic numbers were just sequential numbers based on an element's atomic weight. Moseley's discovery showed that atomic numbers had an experimentally measurable basis. > Thus Moseley placed [|argon] (Z=18) before [|potassium] (Z=19) based on their X-ray wavelengths, despite the fact that argon has a greater atomic weight (39.9) than potassium (39.1). The new order agrees with the chemical properties of these elements, since argon is a [|noble gas] and potassium an [|alkali metal]. Similarly, Moseley placed [|cobalt] before [|nickel], and was able to explain that [|tellurium] occurs before [|iodine] without revising the experimental atomic weight of tellurium (127.6) as proposed by Mendeleev. > Moseley's research also showed that there were gaps in his table at atomic numbers 43 and 61 which are now known to be [|Technetium] and [|Promethium], respectively, both [|radioactive] and not naturally occurring. Following in the footsteps of Dmitri Mendeleev, Henry Moseley also predicted new elements.

[[|edit]] Glenn T. Seaborg
During his Manhattan Project research in 1943 [|Glenn T. Seaborg] experienced unexpected difficulty isolating [|Americium] (95) and [|Curium] (96). He began wondering if these elements more properly belonged to a different series which would explain why the expected chemical properties of the new elements were different. In 1945, he went against the advice of colleagues and proposed a significant change to Mendeleev's table: the [|actinoid series] (previously called the actinide series). > Seaborg's [|actinide concept] of heavy element electronic structure, predicting that the actinides form a transition series analogous to the rare earth series of lanthanide elements, is now well accepted in the scientific community and included in all standard configurations of the periodic table. The actinide series are the second row of the f-block (5f series) and comprise the elements from Actinium to Lawrencium. Seaborg's subsequent elaborations of the actinide concept theorized a series of superheavy elements in a transactinide series comprising elements 104 through 121 and a superactinide series inclusive of elements 122 through 153. > > ** Main discovery periods ** > > > > Reference： > most of the informations are get from the [] > pictures are from [|www.google.com] and [|www.baidu.com]
 * Before 1800 (36 elements): dicoveries during and before the [|age of enlightenment].
 * 1800-1849 (+22 elements): impulse from [|scientific] and [|industrial] revolutions.
 * 1850-1899 (+23 elements): the age of [|classifying elements] received an impulse from the [|spectrum analysis]. Boisbaudran, Bunsen, Crookes, Kirchhoff, and others "hunting [|emission line] signatures".
 * 1900-1949 (+13 elements): impulse from the [|old quantum theory] and [|quantum mechanics].
 * 1950-1999 (+15 elements): "[|atomic bomb]" and [|Particle physics] issues, for atomic numbers 97 and above.