2.4+Organization+of+the+Periodic+Table


 * [[image:cientifico[1].gif]]periodic table, A BRIEF HISTORY OF THE DEVELOPMENT OF PERIODIC TABLE

Although Dmitri Mendeleev is often considered the "father" of the periodic table, the work of many scientists contributed to its present form.**



In the Beginning
A necessary prerequisite to the construction of the periodic table was the discovery of the individual elements. Although elements such as gold, silver, tin, copper, lead and mercury have been known since antiquity, the first scientific discovery of an element occurred in 1649 when Hennig Brand discovered phosphorous. During the next 200 years, a vast body of knowledge concerning the properties of elements and their compounds was acquired by chemists ([|view] a 1790 article on the elements). By 1869, a total of 63 elements had been discovered. As the number of known elements grew, scientists began to recognize patterns in properties and began to develop classification schemes.

Law of Triads
In 1817 Johann Dobereiner noticed that the atomic weight of strontium fell midway between the weights of calcium and barium, elements possessing similar chemical properties. In 1829, after discovering the halogen triad composed of chlorine, bromine, and iodine and the alkali metal triad of lithium, sodium and potassium he proposed that nature contained triads of elements the middle element had properties that were an average of the other two members when ordered by the atomic weight (the Law of Triads).

This new idea of triads became a popular area of study. Between 1829 and 1858 a number of scientists (Jean Baptiste Dumas, Leopold Gmelin, Ernst Lenssen, Max von Pettenkofer, and J.P. Cooke) found that these types of chemical relationships extended beyond the triad. During this time fluorine was added to the halogen group; oxygen, sulfur,selenium and tellurium were grouped into a family while nitrogen, phosphorus, arsenic, antimony, and bismuth were classified as another. Unfortunately, research in this area was hampered by the fact that accurate values of were not always available.

First Attempts At Designing a Periodic Table
If a periodic table is regarded as an ordering of the chemical elements demonstrating the periodicity of chemical and physical properties, credit for the first periodic table (published in 1862) probably should be given to a French geologist, A.E.Beguyer de Chancourtois. De Chancourtois transcribed a list of the elements positioned on a cylinder in terms of increasing atomic weight. When the cylinder was constructed so that 16 mass units could be written on the cylinder per turn, closely related elements were lined up vertically. This led de Chancourtois to propose that "the properties of the elements are the properties of numbers." De Chancourtois was first to recognize that elemental properties reoccur every seven elements, and using this chart, he was able to predict the the stoichiometry of several metallic oxides. Unfortunately, his chart included some ions and compounds in addition to elements.

Law of Octaves
[|John Newlands], an English chemist, wrote a paper in 1863 which classified the 56 established elements into 11 groups based on similar physical properties, noting that many pairs of similar elements existed which differed by some multiple of eight in atomic weight. In 1864 Newlands published his version of the periodic table and proposed the Law of Octaves (by analogy with the seven intervals of the musical scale). This law stated that any given element will exhibit analogous behavior to the eighth element following it in the table.

Who Is The Father of the Periodic Table?
There has been some disagreement about who deserves credit for being the "father" of the periodic table, the German Lothar Meyer (pictured here) or the Russian Dmitri Mendeleev. Both chemists produced remarkably similar results at the same time working independently of one another. Meyer's 1864 textbook included a rather abbreviated version of a periodic table used to classify the elements. This consisted of about half of the known elements listed in order of their atomic weight and demonstrated periodic valence chages as a function of atomic weight. In 1868, Meyer constructed an extended [|table] which he gave to a colleague for evaluation. Unfortunately for Meyer, Mendeleev's table became available to the scientific community via publication (1869) before Meyer's appeared (1870).

Dmitri Ivanovich Mendeleev (1834-1907), the youngest of 17 children was born in the Siberian town of Tobol'sk where his father was a teacher of Russian literature and philosophy (portrait by Ilyia Repin). Mendeleev was not considered an outstanding student in his early education partly due to his dislike of the classical languages that were an important educational requirement at the time even though he showed prowess in mathematics and science. After his father's death, he and his mother moved to St. Petersburg to pursue a university education. After being denied admission to both the University of Moscow and St. Petersburg University because of his provincial background and unexceptional academic background, he finally earned a place at the Main Pedagogical Institute (St. Petersburg Institute). Upon graduation, Mendeleev took a position teaching science in a gymnasium. After a time as a teacher, he was admitted to graduate work at St. Petersburg University where he earned a Master's degree in 1856. Mendeleev so impressed his instructors that he was retained to lecture in chemistry. After spending 1859 and 1860 in Germany furthering his chemical studies, he secured a position as professor of chemistry at St. Petersburg University, a position he retained until 1890. While writing a textbook on systematic inorganic chemistry, //Principles of Chemistry//, which appeared in thirteen editions the last being in 1947, Mendeleev organized his material in terms of the families of the known elements which displayed similar properties. The first part of the text was devoted to the well known chemistry of the halogens. Next, he chose to cover the chemistry of the metallic elements in order of combining power -- alkali metals first (combining power of one), alkaline earths (two), etc. However, it was difficult to classify metals such as copper and mercury which had multiple combining powers, sometimes one and other times two. While tryuing to sort out this dilema, Mendeleev noticed patterns in the properties and atomic weights of halogens, alkali metals and alkaline metals. He observed similarities between the series Cl-K-Ca, Br-/Rb-Sr and I-Cs-Ba. In an effort to extend this pattern to other elements, he created a card for each of the 63 known elements. Each card contained the element's symbol, atomic weight and its characteristic chemical and physical properties. When Mendeleev arranged the cards on a table in order of ascending atomic weight grouping elements of similar properties together in a manner not unlike the card arrangement in his favorite solitare card game, patience, the periodic table was formed. From this table, Mendeleev developed his statement of the periodic law and published his work [|//On the Relationship of the Properties of the Elements to their Atomic Weights//]in 1869. The advantage of Mendeleev's table over previous attempts was that it exhibited similarities not only in small units such as the triads, but showed similarities in an entire network of vertical, horizontal, and diagonal relationships. In 1906, Mendeleev came within one vote of being awarded the Nobel Prize for his work.

At the time that Mendeleev developed his periodic table since the experimentally determined atomic masses were not always accurate, he reordered elements despite their accepted masses. For example, he changed the weight of beryllium from 14 to 9. This placed beryllium into Group 2 above magnesium whose properties it more closely resembled than where it had been located above nitrogen. In all Mendeleev found that 17 elements had to be moved to new positions from those indicated strictly by atomic weight for their properties to correlate with other elements. These changes indicated that there were errors in the accepted atomic weights of some elements (atomic weights were calculated from combining weights, the weight of an element that combines with a given weight of a standard.) However, even after corrections were made by redetermining atomic weights, some elements still needed to be placed out of order of their atomic weights. From the gaps present in his table, Mendeleev predicted the existence and properties of unknown elements which he called eka-aluminum, eka-boron, and eka-silicon. The elements gallium, scandium and germanium were found later to fit his predictions quite well. In addition to the fact that Mendeleev's table was published before Meyers', his work was more extensive predicting new or missing elements. In all Mendeleev predicted the existence of 10 new elements, of which seven were eventually discovered -- the other three, atomic weights 45, 146 and 175 do not exist. He also was incorrect in suggesting that the element pairs of argon-potassium, cobalt-nickel and tellurium-iodine should be interchanged in position due to inaccurate atomic weights. Although these elements did need to be interchanged, it was because of a flaw in the reasoning that periodicity is a function of atomic weight.

Discovery of the Noble Gases
In 1895 [|Lord Rayleigh] reported the discovery of a new gaseous element named argon which proved to be chemically inert. This element did not fit any of the known periodic groups. In 1898, [|William Ramsey] suggested that argon be placed into the periodic table between chlorine and potassium in a family with helium, despite the fact that argon's atomic weight was greater than that of potassium. This group was termed the "zero" group due to the zero valency of the elements. Ramsey accurately predicted the future discovery and properties neon.

Atomic Structure and the Periodic Table
Although Mendeleev's table demonstrated the periodic nature of the elements, it remained for the discoveries of scientists of the 20th Century to explain why the properties of the elements recur periodically.

In 1911 [|Ernest Rutherford] published studies of the scattering of alpha particles by heavy atom nuclei which led to the determination of nuclear charge. He demonstrated that the nuclear charge on a nucleus was proportional to the atomic weight of the element. Also in 1911, A. van den Broek in a series of two papers proposed that the atomic weight of an element was approximately equal to the charge on an atom. This charge, later termed the atomic number, could be used to number the elements within the periodic table. In 1913, Henry Moseley ([|see a picture]) published the results of his measurements of the wavelengths of the x-ray spectral lines of a number of elements which showed that the ordering of the wavelengths of the x-ray emissions of the elements coincided with the ordering of the elements by atomic number. With the discovery of isotopes of the elements, it became apparent that atomic weight was not the significant player in the periodic law as Mendeleev, Meyers and others had proposed, but rather, the properties of the elements varied periodically with atomic number.

The question of why the periodic law exists was answered as scientists developed an understanding of the electronic structure of the elements beginning with Niels Bohr's studies of the organization of electrons into shells through G.N. Lewis' ([|see a picture]) discoveries of bonding electron pairs.

The Modern Periodic Table
The last major changes to the periodic table resulted from Glenn Seaborg's work in the middle of the 20th Century. Starting with his discovery of plutonium in 1940, he discovered all the transuranic elements from 94 to 102. He reconfigured the periodic table by placing the actinide series below the lanthanide series. In 1951, Seaborg was awarded the [|Nobel Prize] in chemistry for his work. Element 106 has been named seaborgium (Sg) in his honor.

is a systematic arrangement of the chemical elements. An earlier version was devised in 1869 by Dmitrii Ivanovich Mendeleev (Russian chemist, 1834-1907). By arranging the elements in order of their atomic weights, he was able to show relationships, such as valency, that occurred at regular intervals and was able to predict the properties of elements still undiscovered in the nineteenth century.

take to the free dictionary taken from www.wou.edu

** Organization of the Periodic Table **
 * Topics: ** **Lewis Dot Structures, Ionization Energy, Electronegativity**
 * Aim **** : ** What is the relationship between ionization energy and electronegativity?
 * Do Now **** : ** On today's handout. (Review of Lewis Dot Structures and electronegativity).

SWR: Electronegativitity, Lewis Dot Structures, properties of transition metals and noble gases. SWBAT: Define electronegativity, define ionization energy, identify elements with high and low values of each, compare ionization energy to electronegativity and understand the basis for bonding.
 * Behavioral Objectives **** : **

**periodic table,** chart of the elements arranged according to the [|periodic law] **periodic law,** statement of a periodic recurrence of chemical and physical properties of the elements when the elements are arranged in order of increasing atomic number. (showing atomic number and atomic symbol; click on atomic symbol for more detailed information)
 * Motivation **** : ** A fictional story which creates an analogy to the process of the loss and gain of electrons and ultimately bonding. The story is in a language that the students should be able to easily absorb and creates a macro level context for microscopic concepts.
 * .....** ** Click the link for more information. ** discovered by Dmitri I. [|Mendeleev]  **Mendeleev, Dmitri Ivanovich** (mĕndəlā`əf, Rus.
 * .....** ** Click the link for more information. ** and revised by Henry G. J. [|Moseley]  **Moseley, Henry Gwyn Jeffreys** (mōz`lē), 1887–1915, English physicist, grad. Trinity College, Oxford, 1910.
 * .....** ** Click the link for more information. ** . In the periodic table the elements are arranged in columns and rows according to increasing [|atomic number]  **atomic number,** often represented by the symbol //Z,// the number of protons in the nucleus of an atom, as well as the number of electrons in the neutral atom. Atoms with the same atomic number make up a chemical element.
 * .....** ** Click the link for more information. ** (see the table entitled [|Periodic Table] Periodic Table of the Elements

[] Groups There are 18 vertical columns, or groups, in the standard periodic table. At present, there are three versions of the periodic table, each with its own unique column headings, in wide use. The three formats are the old International Union of Pure and Applied Chemistry (IUPAC) table, the Chemical Abstract Service (CAS) table, and the new IUPAC table. The old IUPAC system labeled columns with Roman numerals followed by either the letter A or B. Columns 1 through 7 were numbered IA through VIIA, columns 8 through 10 were labeled VIIIA, columns 11 through 17 were numbered IB through VIIB and column 18 was numbered VIII. The CAS system also used Roman numerals followed by an A or B. This method, however, labeled columns 1 and 2 as IA and IIA, columns 3 through 7 as IIIB through VIB, column 8 through 10 as VIII, columns 11 and 12 as IB and IIB and columns 13 through 18 as IIIA through VIIIA. However, in the old IUPAC system the letters A and B were designated to the left and right part of the table, while in the CAS system the letters A and B were designated to the main group elements and transition elements respectively. (The preparer of the table arbitrarily could use either an upper-or lower-case letter A or B, adding to the confusion.) Further, the old IUPAC system was more frequently used in Europe while the CAS system was most common in America. In the new IUPAC system, columns are numbered with Arabic numerals from 1 to 18. These group numbers correspond to the number of //s,// //p,// and //d// orbital electrons added since the last noble gas element (in column 18). This is in keeping with current interpretations of the periodic law which holds that the elements in a group have similar configurations of the outermost electron shells of their atoms. Since most chemical properties result from outer electron interactions, this tends to explain why elements in the same group exhibit similar physical and chemical properties. Unfortunately, the system fails for the elements in the first 3 periods (or rows; see below). For example, aluminum, in the column numbered 13, has only 3 //s,// //p,// and //d// orbital electrons. Nevertheless, the American Chemical Society has adopted the new IUPAC system. The horizontal rows of the table are called periods. The elements of a period are characterized by the fact that they have the same number of electron shells; the number of electrons in these shells, which equals the element's atomic number, increases from left to right within each period. In each period the lighter metals appear on the left, the heavier metals in the center, and the nonmetals on the right. Elements on the borderline between metals and nonmetals are called metalloids. Group 1 (with one valence electron) and Group 2 (with two valence electrons) are called the [|alkali metals] **alkali metals,** metals found in Group 1 of the periodic table. Compared to other metals they are soft and have low melting points and densities. Alkali metals are powerful reducing agents and form univalent compounds. In a relatively simple type of periodic table, each position gives the name and chemical symbol for the element assigned to that position; its atomic number; its [|atomic weight] **atomic weight,** mean (weighted average) of the masses of all the naturally occurring isotopes of a chemical element, as contrasted with atomic mass , which is the mass of any individual isotope.
 * .....** ** Click the link for more information. ** ).
 * .....** ** Click the link for more information. ** and the [|alkaline-earth metals]  **alkaline-earth metals,** metals constituting Group 2 of the periodic table . Generally, they are softer than most other metals, react readily with water (especially when heated), and are powerful reducing agents, but they are exceeded in each of these properties by the
 * .....** ** Click the link for more information. **, respectively. Two series of elements branch off from Group 3, which contains the [|transition elements]  **transition elements** or **transition metals,** in chemistry, group of elements characterized by the filling of an inner //d// electron orbital as atomic number increases.
 * .....** ** Click the link for more information. **, or transition metals; elements 57 to 71 are called the [|lanthanide series]  **lanthanide series,** a series of metallic elements, included in the rare-earth metals , in Group 3 of the periodic table . Members of the series are often called lanthanides, although lanthanum (atomic number 57) is not always considered a member of the series.
 * .....** ** Click the link for more information. **, or rare earths, and elements 89 to 103 are called the [|actinide series]  **actinide series,** a series of radioactive metallic elements in Group 3 of the periodic table . Members of the series are often called actinides, although actinium (at. no. 89) is not always considered a member of the series.
 * .....** ** Click the link for more information. **, or radioactive rare earths; a third set, the superactinide series (elements 122–153), is predicted to fall outside the main body of the table, but none of these has yet been synthesized or isolated. The nonmetals in Group 17 (with seven valence electrons) are called the [|halogens]  **halogen** (hăl`əjĕn) [Gr.
 * .....** ** Click the link for more information. ** . The elements grouped in the final column (Group 18) have no valence electrons and are called the [|inert gases]  **inert gas** or **noble gas,** any of the elements in Group 18 of the periodic table . In order of increasing atomic number they are: helium, neon , argon , krypton , xenon , and radon.
 * .....** ** Click the link for more information. **, or noble gases, because they react chemically only with extreme difficulty.
 * .....** ** Click the link for more information. ** (the weighted average of the masses of its stable isotopes, based on a scale in which carbon-12 has a mass of 12); and its electron configuration, i.e., the distribution of its electrons by shells. The only exceptions are the positions of elements 103 through 118; complete information on these elements has not been compiled. Larger and more complicated periodic tables may also include the following information for each element: atomic diameter or radius; common valence numbers or oxidation states; melting point; boiling point; density; specific heat; Young's modulus; the quantum states of its valence electrons; type of crystal form; stable and radioactive isotopes; and type of magnetism exhibited by the element (paramagnetism or diamagnetism).

S1a: Demonstrates an understanding of the structure of atoms S1f: Demonstrates an understanding of interactions of energy and matter
 * NYC Science Standards **** : **

Program Standard A: Teaching practices need to be consistent with the goals and curriculum framework. Teaching standard A: Select teaching and assessment strategies that support the development of student understanding and nurture a community of science learners. Teaching Standard B: Teachers of science guide and facilitate learning.
 * National Science Standards: **


 * Materials **** : ** Today's handouts. Reference tables.


 * Vocabulary **** : ** Electronegativity, ionization energy, Lewis Dot Structures.

Taken from http://www.scienceteacherprogram.org/chemistry/Clark2004.html

In 1789, building upon the work of precursors and contemporaries alike, the French chemist Antoine Laurent Lavoisier first defined an element as a fundamental substance that could not be broken down by any chemical means then known. In the same //Treatise on Chemical Elements,// he compiled a list of 33 elements (a number of which were not actually elements) and devised a naming system for the discovery of new elements.

**,**

H: Hydrogen He: Helium Li: Lithium Be: Beryllium B: Boron C: Carbon N: Nitrogen O: Oxygen F : Fluorine Ne: Neon Na: Sodium Mg: Magnesium Al: Aluminium Si: Silicon P: Phosphorus S: Sulfur Cl: Chlorine Ar: Argon K : Potassium Ca: Calcium Sc: Scandium

Ti: Titanium V: Vanadium Cr: Chromium Mn: Manganese Fe: Iron Co: Cobalt Ni: Nickel Cu: Copper Zn: Zinc Ga : Gallium Ge : Germanium As : Arsenic Se: Selenium Br: Bromine Kr: Krypton Rb: Rubidium Sr: Strontium Y: Yttrium Zr: Zirconium Nb: Niobium Mo: Molybdenum Tc: Technetium Ru: Ruthenium Rh: Rhodium Pd: Palladium Ag : Silver Cd: Cadmium In: Indium Sn: Tin Sb: Antimony Te: Tellurium I: Iodine Xe: Xenon Cs: Caesium Ba: Barium La: Lanthanum Hf: Hafnium Ta: Tantalum W: Tungsten Re: Rhenium Os: Osmium Ir: Iridium Pt: Platinum Au: Gold Hg: Mercury Tl: Thallium Pb: Lead Bi: Bismuth Po: Polonium At: Astatine Rn: Radon Fr : Francium Ra: Radium Ac: Actinium Rf: Rutherfordium Db: Dubnium Sg : Seaborgium Bh: Bohrium Hs: Hassium Mt: Meitnerium Uup: Ununpentium Uuh: Ununhexium Uuq: Ununquadium Uuo: Ununoctium Uut: Ununtrium Ce: Cerium Pr: Praseodymium Nd: Neodymium Pm: Prometium Sm: Samarium Eu: Europium Gd: Gadolinium Tb: Terbium Dy: Dysprosium Ho: Holmium Er: Erbium Tm: Thulium Yb: Ytterbium Lu: Lutetium Th : Thorium Pa: Protactinium U: Uranium Np: Neptunium Pu: Plutonium Am: Americium Cm: Curium Bk: Berkelium Cf: Californium Es: Einstenium Fm: Fermium Md: Mendelevium No: Nobelium Lr: Lawrencium

In honour of scientist and astronomer Nicolaus Copernicus (1473-1543), the discovering team around Professor Sigurd Hofmann suggested the name **copernicium** with the element symbol **Cn** (original suggestion was Cp) for the new element 112, discovered at the GSI Helmholtzzentrum für Schwerionenforschung (Center for Heavy Ion Research) in Darmstadt. It was Copernicus who discovered that the Earth orbits the Sun, thus paving the way for our modern view of the world. Thirteen years ago, element 112 was discovered by an international team of scientists at the GSI accelerator facility. The International Union of Pure and Applied Chemistry, IUPAC, recently confirmed their discovery. IUPAC has now confirmed the new element's name as copernicium. The modern definition of chemistry Classically, before the 20th century, chemistry was defined as the science of the nature of matter and its transformations. It was therefore clearly distinct from physics which was not concerned with such dramatic transformation of matter. Moreover, in contrast to physics, chemistry was not using much of mathematics. Even some were particularly reluctant to using mathematics within chemistry. For example, Auguste Comte wrote in 1830:

Every attempt to employ mathematical methods in the study of chemical questions must be considered profoundly irrational and contrary to the spirit of chemistry.... if mathematical analysis should ever hold a prominent place in chemistry -- an aberration which is happily almost impossible -- it would occasion a rapid and widespread degeneration of that science. However, in the second part of the 19th century, the situation changed and August Kekule wrote in 1867:

I rather expect that we shall someday find a mathematico-mechanical explanation for what we now call atoms which will render an account of their properties. of the atomic structure in 1912, and, scientists had to change their viewpoint on the nature of matter. The experience acquired by chemists was no longer pertinent to the study of the whole nature of matter but only to aspects related to the surrounding the atomic and the movement of the latter in the induced by the former (see The range of chemistry was thus restricted to the nature of matter around us in conditions which are not too far (or exceptionally far) from and in cases where the exposure to radiation is not too different from the natural ] radiations on Earth. Chemistry was therefore re-defined as the science of matter that deals with the composition, structure, and properties of substances and with the transformations that they undergo.] However the meaning of matter used here relates explicitly to substances made of atoms and molecules, disregarding the matter within the atomic nuclei and its nuclear reaction or matter within highly ionized plasmas. This does not mean that chemistry is never involved with plasma or nuclear sciences or even bosonic fields nowadays, since areas such as Quantum Chemistry and Nuclear Chemistry are currently well developed and formally recognized sub-fields of study under the Chemical sciences (Chemistry), but what is now formally recognized as subject of study under the Chemistry category as a science is always based on the use of concepts that describe or explain phenomena either from matter or to matter in the atomic or molecular scale, including the study of the behavior of many molecules as an aggregate or the study of the effects of a single proton on an single atom, but excluding phenomena that deal with different types of matter (e.g. Bose-Einstein condensate, Higgs Boson, dark matter, naked singularity, etc.) and excluding principles that refer to intrinsic abstract laws of nature in which their concepts can be formulated completely without a precise formal molecular or atomic paradigmatic view Nevertheless the field of chemistry is still, on our human scale, very broad and the claim that //chemistry is everywhere// is accurate.

The periodic table is the most imp

tatortant chemistry reference there is//.// It arranges all the known elements in an informative array. Elements are arranged left to right and top taken from www.web**elements**.com

periodic table ​ The **periodic table of the chemical elements** (also **Mendeleev's table**, **periodic table of the elements** or just **periodic table**) is a display of the. Although precursors to this table exist, its invention is generally credited to Russian chemist 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 providing an extremely useful framework to classify, systematize, and compare all of the many different forms of behavior. The table has found wide application in and especially. The current standard table contains 117 elements as of July 2009. taken from []



organization of the periodic table ==

The Periodic table is designed to help you predict what an element's physical and chemical properties are. You can also predict what elements will bond with each other. First, let's look at the columns and rows of the periodic table.



Periodic Table Courtesy of Periodic Table of the Elements v. 4.0 by Kostas Tsigaridis [|(http://ptoe.move.to/)]
The vertical columns of the periodic table (there are 18) are called groups or families. Elements in the same group or family have similar but not identical characteristics. You will learn more about the 18 groups in a later section. You can know properties of a certain element by knowing which group it belongs to. The horizontal rows of the periodic table are called periods. Elements in a period are not alike in properties. As a rule, the first element in a period is usually an active solid, and the last element in a period is always an inactive gas. Atomic size decreases from left to right across a period, but atomic mass increases from left to right across a period. Atoms on the left of the period, therefore, are usually larger and more lightweight than the smaller, heavier atoms on the right of the period. When you look at the periodic table, you should notice that each box represents a different element, and each box contains vital information about the element, including its name, symbol, atomic number, and atomic mass. Look at the sample box below for a description of each of these pieces of information. = C =
 * __ Groups or Families __**
 * __Periods __**
 * __ Think Inside the Box __**
 * ===6===

Carbon
12.011 || The top number is the **__atomic number__**. Every element has its own unique atomic number. The atomic number tells how many protons are in one atom of that element. Since no two elements have the same atomic number, no two elements have the same number of protons. The large letter is the element's symbol, and just below that is the element's name. Each element has its own unique symbol and name. It is often very useful to memorize symbols and names for elements, especially the more commonly used elements. Below the name is the element's **__atomic mass__**. The atomic mass is the mass in atomic mass units for all possible isotopes of that element. The atomic mass essentially gives you an estimate of how massive one atom of that element is.

taken from: []

PERIODIC TABLE

Chart of the elements arranged according to the [|periodic law]  periodic law, statement of a periodic recurrence of chemical and physical properties of the elements when the elements are arranged in order of increasing atomic number.

Groups There are 18 vertical columns, or groups, in the standard periodic table. At present, there are three versions of the periodic table, each with its own unique column headings, in wide use. The three formats are the old International Union of Pure and Applied Chemistry (IUPAC) table, the Chemical Abstract Service (CAS) table, and the new IUPAC table. The old IUPAC system labeled columns with Roman numerals followed by either the letter A or B. Columns 1 through 7 were numbered IA through VIIA, columns 8 through 10 were labeled VIIIA, columns 11 through 17 were numbered IB through VIIB and column 18 was numbered VIII. The CAS system also used Roman numerals followed by an A or B. This method, however, labeled columns 1 and 2 as IA and IIA, columns 3 through 7 as IIIB through VIB, column 8 through 10 as VIII, columns 11 and 12 as IB and IIB and columns 13 through 18 as IIIA through VIIIA. However, in the old IUPAC system the letters A and B were designated to the left and right part of the table, while in the CAS system the letters A and B were designated to the main group elements and transition elements respectively. (The preparer of the table arbitrarily could use either an upper-or lower-case letter A or B, adding to the confusion.) Further, the old IUPAC system was more frequently used in Europe while the CAS system was most common in America. In the new IUPAC system, columns are numbered with Arabic numerals from 1 to 18. These group numbers correspond to the number of //s,// //p,// and //d// orbital electrons added since the last noble gas element (in column 18). This is in keeping with current interpretations of the periodic law which holds that the elements in a group have similar configurations of the outermost electron shells of their atoms. Since most chemical properties result from outer electron interactions, this tends to explain why elements in the same group exhibit similar physical and chemical properties. Unfortunately, the system fails for the elements in the first 3 periods (or rows; see below). For example, aluminum, in the column numbered 13, has only 3 //s,// //p,// and //d// orbital electrons. Nevertheless, the American Chemical Society has adopted the new IUPAC system. The horizontal rows of the table are called periods. The elements of a period are characterized by the fact that they have the same number of electron shells; the number of electrons in these shells, which equals the element's atomic number, increases from left to right within each period. In each period the lighter metals appear on the left, the heavier metals in the center, and the nonmetals on the right. Elements on the borderline between metals and nonmetals are called metalloids. Group 1 (with one valence electron) and Group 2 (with two valence electrons) are called the [|alkali metals] alkali metals, metals found in Group 1 of the periodic table. Compared to other metals they are soft and have low melting points and densities. Alkali metals are powerful reducing agents and form univalent compounds. and the [|alkaline-earth metals] alkaline-earth metals, metals constituting Group 2 of the periodic table. Generally, they are softer than most other metals, react readily with water (especially when heated), and are powerful reducing agents, but they are exceeded in each of these properties by the , respectively. Two series of elements branch off from Group 3, which contains the [|transition elements] transition elements or transition metals, in chemistry, group of elements characterized by the filling of an inner //d// electron orbital as atomic number increases. , or transition metals; elements 57 to 71 are called the [|lanthanide series] lanthanide series, a series of metallic elements, included in the rare-earth metals, in Group 3 of the periodic table. Members of the series are often called lanthanides, although lanthanum (atomic number 57) is not always considered a member of the series. The elements grouped in the final column (Group 18) have no valence electrons and are called the [|inert gases] inert gas or noble gas, any of the elements in Group 18 of the periodic table. In order of increasing atomic number they are: helium, neon , argon , krypton , xenon , and radon. ., or noble gases, because they react chemically only with extreme difficulty. In a relatively simple type of periodic table, each position gives the name and chemical symbol for the element assigned to that position; its atomic number; its [|atomic weight] atomic weight, mean (weighted average) of the masses of all the naturally occurring isotopes of a chemical element, as contrasted with atomic mass , which is the mass of any individual isotope. (the weighted average of the masses of its stable isotopes, based on a scale in which carbon-12 has a mass of 12); and its electron configuration, i.e., the distribution of its electrons by shells. The only exceptions are the positions of elements 103 through 118; complete information on these elements has not been compiled. Larger and more complicated periodic tables may also include the following information for each element: atomic diameter or radius; common valence numbers or oxidation states; melting point; boiling point; density; specific heat; Young's modulus; the quantum states of its valence electrons; type of crystal form; stable and radioactive isotopes; and type of magnetism exhibited by the element (paramagnetism or diamagnetism). periodic table, chart of the elements arranged according to the periodic law periodic law, statement of a periodic recurrence of chemical and physical properties of the elements when the elements are arranged in order of increasing atomic number. ..... Click the link for more information. discovered by Dmitri I. Mendeleev Mendeleev, Dmitri Ivanovich (mĕndəlā`əf, Rus. ..... Click the link for more information. and revised by Henry G. J. Moseley Moseley, Henry Gwyn Jeffreys (mōz`lē), 1887–1915, English physicist, grad. Trinity College, Oxford, 1910. ..... Click the link for more information. . In the periodic table the elements are arranged in columns and rows according to increasing atomic number atomic number, often represented by the symbol Z, the number of protons in the nucleus of an atom, as well as the number of electrons in the neutral atom. Atoms with the same atomic number make up a chemical element . ..... Click the link for more information. (see the table entitled Periodic Table Periodic Table of the Elements (showing atomic number and atomic symbol; click on atomic symbol for more detailed information)
 * .....** Click the link for more information., or rare earths, and elements 89 to 103 are called the [|actinide series]  actinide series, a series of radioactive metallic elements in Group 3 of the periodic table . Members of the series are often called actinides, although actinium (at. no. 89) is not always considered a member of the series.
 * .....** Click the link for more information., or radioactive rare earths; a third set, the superactinide series (elements 122–153), is predicted to fall outside the main body of the table, but none of these has yet been synthesized or isolated. The nonmetals in Group 17 (with seven valence electrons) are called the [|halogens]  halogen (hăl`əjĕn) [Gr.

Groups ..... Click the link for more information. ). There are 18 vertical columns, or groups, in the standard periodic table. At present, there are three versions of the periodic table, each with its own unique column headings, in wide use. The three formats are the old International Union of Pure and Applied Chemistry (IUPAC) table, the Chemical Abstract Service (CAS) table, and the new IUPAC table. The old IUPAC system labeled columns with Roman numerals followed by either the letter A or B. Columns 1 through 7 were numbered IA through VIIA, columns 8 through 10 were labeled VIIIA, columns 11 through 17 were numbered IB through VIIB and column 18 was numbered VIII. The CAS system also used Roman numerals followed by an A or B. This method, however, labeled columns 1 and 2 as IA and IIA, columns 3 through 7 as IIIB through VIB, column 8 through 10 as VIII, columns 11 and 12 as IB and IIB and columns 13 through 18 as IIIA through VIIIA. However, in the old IUPAC system the letters A and B were designated to the left and right part of the table, while in the CAS system the letters A and B were designated to the main group elements and transition elements respectively. (The preparer of the table arbitrarily could use either an upper-or lower-case letter A or B, adding to the confusion.) Further, the old IUPAC system was more frequently used in Europe while the CAS system was most common in America. In the new IUPAC system, columns are numbered with Arabic numerals from 1 to 18. These group numbers correspond to the number of s, p, and d orbital electrons added since the last noble gas element (in column 18). This is in keeping with current interpretations of the periodic law which holds that the elements in a group have similar configurations of the outermost electron shells of their atoms. Since most chemical properties result from outer electron interactions, this tends to explain why elements in the same group exhibit similar physical and chemical properties. Unfortunately, the system fails for the elements in the first 3 periods (or rows; see below). For example, aluminum, in the column numbered 13, has only 3 s, p, and d orbital electrons. Nevertheless, the American Chemical Society has adopted the new IUPAC system. The horizontal rows of the table are called periods. The elements of a period are characterized by the fact that they have the same number of electron shells; the number of electrons in these shells, which equals the element's atomic number, increases from left to right within each period. In each period the lighter metals appear on the left, the heavier metals in the center, and the nonmetals on the right. Elements on the borderline between metals and nonmetals are called metalloids. Group 1 (with one valence electron) and Group 2 (with two valence electrons) are called the alkali metals alkali metals, metals found in Group 1 of the periodic table. Compared to other metals they are soft and have low melting points and densities. Alkali metals are powerful reducing agents and form univalent compounds. ..... Click the link for more information. and the alkaline-earth metals alkaline-earth metals, metals constituting Group 2 of the periodic table. Generally, they are softer than most other metals, react readily with water (especially when heated), and are powerful reducing agents, but they are exceeded in each of these properties by the ..... Click the link for more information. , respectively. Two series of elements branch off from Group 3, which contains the transition elements transition elements or transition metals, in chemistry, group of elements characterized by the filling of an inner d electron orbital as atomic number increases. ..... Click the link for more information. , or transition metals; elements 57 to 71 are called the lanthanide series lanthanide series, a series of metallic elements, included in the rare-earth metals, in Group 3 of the periodic table. Members of the series are often called lanthanides, although lanthanum (atomic number 57) is not always considered a member of the series. ..... Click the link for more information. , or rare earths, and elements 89 to 103 are called the actinide series actinide series, a series of radioactive metallic elements in Group 3 of the periodic table. Members of the series are often called actinides, although actinium (at. no. 89) is not always considered a member of the series. ..... Click the link for more information. , or radioactive rare earths; a third set, the superactinide series (elements 122–153), is predicted to fall outside the main body of the table, but none of these has yet been synthesized or isolated. The nonmetals in Group 17 (with seven valence electrons) are called the halogens halogen (hăl`əjĕn) [Gr. ..... Click the link for more information. . The elements grouped in the final column (Group 18) have no valence electrons and are called the inert gases inert gas or noble gas, any of the elements in Group 18 of the periodic table. In order of increasing atomic number they are: helium, neon , argon , krypton , xenon , and radon. ..... Click the link for more information. , or noble gases, because they react chemically only with extreme difficulty. In a relatively simple type of periodic table, each position gives the name and chemical symbol for the element assigned to that position; its atomic number; its atomic weight atomic weight, mean (weighted average) of the masses of all the naturally occurring isotopes of a chemical element, as contrasted with atomic mass , which is the mass of any individual isotope. ..... Click the link for more information. (the weighted average of the masses of its stable isotopes, based on a scale in which carbon-12 has a mass of 12); and its electron configuration, i.e., the distribution of its electrons by shells. The only exceptions are the positions of elements 103 through 118; complete information on these elements has not been compiled. Larger and more complicated periodic tables may also include the following information for each element: atomic diameter or radius; common valence numbers or oxidation states; melting point; boiling point; density; specific heat; Young's modulus; the quantum states of its valence electrons; type of crystal form; stable and radioactive isotopes; and type of magnetism exhibited by the element (paramagnetism or diamagnetism). taken from:the free dictionari