| Periodic Table of the Chemical Elements |
| >>Note: The periodic table of the chemical elements is a tabular method of displaying the chemical elements . Although precursors to this table exist, its invention is generally credited to Russian chemist Dmitri Mendeleev in 1869. 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. The table has also found wide application in physics , biology , engineering , and industry . The current standard table contains 117 confirmed elements as of October 16 , 2006 (while element 118 has been synthesized, element 117 has not). |
| [1] IUPAC article on periodic table |
| | Inner transition elements |
| | >>Note: 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 atomic ground state, the highest-energy electrons occupy f-orbitals. |
| | Unlike the other blocks, the conventional divisions of the f-block follow periods of similar atomic number rather than groups of similar electron configuration. Thus, the f-block is divided into the lanthanoid series and the actinoid series. |
| | The name 'inner transition' is derived by analogy with the transition metals. |
| | Like the s-block, the elements of the f-block are highly reactive metals. They catch fire in air very easily, and react with water to liberate hydrogen. Physically they are denser and have higher melting and boiling points than the alkaline earth metals, but their reactivity makes them of very limited use structurally. They are used together to make cigarette lighter flints because they catch fire in air so easily. Most of them are extracted by electrolysis of molten chlorides: the metals are much too reactive to be extractable from aqueous solutions. |
| | The compounds of most f-block elements are ionic salts with M3+ ions, often hydrated in aqueous solutions. Cerium also forms a small series of strongly oxidising compounds with the +4 oxidation state, including ceric oxide (CeO2). The lighter actinides (protactinium to americium) have f-electrons that can participate in bonding and form compounds in a variety of oxidation states from +2 to +6. Owing to the pulling of the inner f-electrons towards the nucleus, the heavier actinides (curium to lawrencium) tend not to use their inner f-electrons and resemble the lanthanides in forming salts with M3+ ions. |
| | [http://en.wikipedia.org/wiki/Inner_transition_element] |
| | >>Note: 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 periodic table can be termed either a metal or a non-metal. (A few elements with intermediate properties are referred to as metalloids.) |
| | The elements generally regarded as nonmetals are: |
| | In Group 15 (the pnictogens): nitrogen (N), phosphorus (P) |
| | Several elements in Group 16, the chalcogens: oxygen (O), sulfur (S), selenium (Se) |
| | All elements in Group 17 - the halogens |
| | All elements in Group 18 - the noble gases |
| | A possible form of periodic table at a pressure of three million atmospheres. It is possible that all the elements become metallic at sufficiently high pressure. The elements C, N, F, Cl, Ne, Ar, Kr, and He (in grey) have not yet been investigated at sufficiently high pressures to achieve metallisation. There is no rigorous definition for the term "nonmetal" - it covers a general spectrum of behaviour. Common properties considered characteristic of a nonmetal include: |
| | poor conductors of heat and electricity when compared to metals |
| | they form acidic oxides (whereas metals generally form basic oxides) |
| | in solid form, they are dull and brittle, rather than metals which are lustrous, ductile or malleable |
| | usually have lower densities than metals |
| | they have significantly lower melting points and boiling points than metals |
| | non-metals have high electronegativity |
| | nonmetals usually have little or no luster |
| | Only eighteen elements in the periodic table are generally considered nonmetals, compared to over eighty metals, but nonmetals make up most of the crust, atmosphere and oceans of the earth. Bulk tissues of living organisms are composed almost entirely of nonmetals. Many nonmetals (hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine) are diatomic, and most of the rest are polyatomic. |
| | Metallisation at huge pressures |
| | Nevertheless, even these 20 elements tend to become metallic at large enough pressures (see nearby periodic table at ~300 GPa). |
| | [http://en.wikipedia.org/wiki/Nonmetal] |
| | >>Note: The alkaline metals are a series of elements comprising Group 1 (IUPAC style) of the periodic table: Lithium (Li),sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). (Note that hydrogen, although nominally also a member of Group 1, very rarely exhibits behavior comparable to the alkali metals). The alkali metals provide one of the best examples of group trends in properties in the periodic table, with well characterized homologous behavior down the group. |
| | The alkali metals are all highly reactive and are rarely found in elemental form in nature. As a result, in the laboratory they are stored under mineral oil. They also tarnish easily and have low melting points and densities. Potassium and rubidium possess a weak radioactive characteristic (harmless) due to the presence of long duration radioactive isotopes. |
| | The alkali metals are silver-colored (cesium has a golden tinge), soft, low-density metals, which react readily with halogens to form ionic salts, and with water to form strongly alkaline (basic) hydroxides. These elements all have one electron in their outermost shell, so the energetically preferred state of achieving a filled electron shell is to lose one electron to form a singly charged positive ion, or cation. |
| | [http://en.wikipedia.org/wiki/Alkali_metal] |
| | >>Note: The alkaline earth metals are a series of elements comprising Group 2 (IUPAC style) of the periodic table: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). The alkaline earth metals provide a good example of group trends in properties in the periodic table, with well characterised homologous behaviour down the group. |
| | The alkaline earth metals are silvery colored, soft, low-density metals, which react readily with halogens to form ionic salts, and with water, though not as rapidly as the alkali metals, to form strongly alkaline (basic) hydroxides. For example, where sodium and potassium react with water at room temperature, magnesium reacts only with steam and calcium with hot water: |
| | Mg + 2 H2O > Mg(OH)2 + H2 |
| | Beryllium is an exception: It does not react with water or steam, and its halides are covalent. |
| | All the alkaline earth metals have two electrons in their outermost shell, so the energetically preferred state of achieving a filled electron shell is to lose two electrons to form doubly charged positive ions. |
| | The alkaline earth metals are named after their oxides, the alkaline earths, whose old-fashioned names were beryllia, magnesia, lime, strontia and baryta. These oxides are basic (alkaline) when combined with water. "Earth" is an old term applied by early chemists to nonmetallic substances that are insoluble in water and resistant to heating--properties shared by these oxides. The realization that these earths were not elements but compounds is attributed to the chemist Antoine Lavoisier. In his Traite Elementaire de Chimie (Elements of Chemistry) of 1789 he called them salt-forming earth elements. Later, he suggested that the alkaline earths might be metal oxides, but admitted that this was mere conjecture. In 1808, acting on Lavoisier's idea, Humphry Davy became the first to obtain samples of the metals by electrolysis of their molten earths. |
| | [http://en.wikipedia.org/wiki/Alkaline_earth_metal] |
| | >>Note: The lanthanoid (according to IUPAC terminology) (previously lanthanide) series comprises the 15 elements with atomic numbers 57 through 71, from lanthanum to lutetium. All lanthanoids are f-block elements, corresponding to the filling of the 4f electron shell, except for lutetium which is a d-block lanthanoid. The lanthanoid series (Ln) is named after lanthanum. |
| | [http://en.wikipedia.org/wiki/Lanthanide] |
| | >>Note: In chemistry, the term transition metal (sometimes also called a transition element) has two possible meanings: |
| | It commonly refers to any element in the d-block of the periodic table, including zinc, cadmium and mercury. This corresponds to groups 3 to 12 on the periodic table. |
| | More strictly, IUPAC defines a transition metal as "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." By this definition, zinc, cadmium, and mercury are excluded from the transition metals, as they have a d10 configuration. Only a few transient species of these elements that leave ions with a partly filled d subshell have been formed, and mercury(I) only occurs as Hg22+, which does not strictly form a lone ion with a partly filled subshell, and hence these three elements are inconsistent with the latter definition. They do form ions with a 2+ oxidation state, but these retain the 4d10 configuration. Element 112 may also be excluded although its oxidation properties are unlikely to be observed due to its radioactive nature. This definition corresponds to groups 3 to 11 on the periodic table. |
| | The first definition is simple and has traditionally been used. However, many interesting properties of the transition elements as a group are the result of their partly filled d subshells. Periodic trends in the d block (transition metals) are less prevailing than in the rest of the periodic table. Going across a period, the valence doesn't change, so the electron being added to an atom goes to the inner shell, not outer shell, strengthening the shield. |
| | The (loosely defined) transition metals are the 40 chemical elements 21 to 30, 39 to 48, 71 to 80, and 103 to 112. The name transition comes from their position in the periodic table of elements. In each of the four periods in which they occur, these elements represent the successive addition of electrons to the d atomic orbitals of the atoms. In this way, the transition metals represent the transition between group 2 elements and group 13 elements. |
| | [http://en.wikipedia.org/wiki/Transition_element] |
| | >>Note: The actinoid (according to IUPAC terminology) (previously actinide) series encompasses the 15 chemical elements that lie between actinium and lawrencium included on the periodic table, with atomic numbers 89 - 103. The actinoid series derives its name from the first element in the series, actinium, and ultimately from the Greek ????? (aktis), "ray," reflecting the elements' radioactivity. |
| | The actinoid series (An) is included in some definitions of the rare earth elements. IUPAC is currently recommending the name actinoid rather than actinide, as the suffix "-ide" generally indicates ions (moreover, from Latin, the suffix -ide means "sons of actinium", while -oid means "similar to actinium"). There are alternative arrangements of the periodic table that exclude actinium or lawrencium from appearing together with the other actinoids. |
| | The actinoids display less similarity in their chemical properties than the lanthanoid series (Ln), exhibiting a wider range of oxidation states, which initially led to confusion as to whether actinium, thorium, and uranium should be considered d-block elements. All actinoids are radioactive. |
| | Only thorium and uranium occur naturally in the earth's crust in anything more than trace quantities. Neptunium and plutonium have been known to show up naturally in trace amounts in uranium ores as a result of decay or bombardment. The remaining actinides were discovered in nuclear fallout, or were synthesized in particle colliders. The latter half of the series possess exceedingly short half-lives. |
| | The actinoids are typically placed below the main body of the periodic table (below the lanthanoid series), in the manner of a footnote. The full-width version of the periodic table shows the position of the actinoids more clearly. |
| | An organometallic compound of an actinoid is known as an organoactinoid. |
| | [http://en.wikipedia.org/wiki/Actinide] |
| | >>Note: In chemistry, a metal (Greek: Metallon) is an element that readily loses electrons to form positive ions (cations) and has metallic bonds between metal atoms. Metals form ionic bonds with non-metals. They are sometimes described as a lattice of positive ions surrounded by a cloud of delocalized electrons. The metals are one of the three groups of elements as distinguished by their ionization and bonding properties, along with the metalloids and nonmetals. On the periodic table, a diagonal line drawn from boron (B) to polonium (Po) separates the metals from the nonmetals. Most elements on this line are metalloids, sometimes called semi-metals; elements to the lower left are metals; elements to the upper right are nonmetals. |
| | [http://en.wikipedia.org/wiki/Metal] |
| | >>Note: 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 in the periodic table can be termed either a metal or a nonmetal - however a few elements with intermediate properties are referred to as metalloids. (In Greek metallon = metal and eidos = sort) |
| | There is no rigorous definition of the term, however the following properties are usually considered characteristic of metalloids: |
| | metalloids often form amphoteric oxides. |
| | metalloids often behave as semiconductors (B,Si,Ge) to semimetals (eg. Sb). |
| | The concepts of metalloid and semiconductor should not be confused. Metalloid refers to the properties of certain elements in relation to the periodic table. Semiconductor refers to the physical properties of materials (including alloys, compounds) and there is only partial overlap between the two. |
| | The following elements are generally considered metalloids: |
| | [http://en.wikipedia.org/wiki/Metalloid] |
| | >>Note: The noble gases are the elements in group 18 (also sometimes Group 0 IUPAC Style, or Group 8) of the periodic table. It is also called helium family or neon family. Chemically, they are very stable due to having the maximum number of valence electrons their outer shell can hold. A thorough explanation requires an understanding of electronic configuration, with references to quantum mechanics. Noble gases rarely react with other elements since they are already stable. Under normal conditions, they occur as odorless, colorless, monatomic gases. Each of them has its melting and boiling point close together, so that only a small temperature range exists for each noble gas in which it is a liquid. Noble gases have numerous important applications in lighting, welding and space technology. The seven noble gasses are: helium, neon, argon, krypton, xenon, radon, and ununoctium. |
| | [http://en.wikipedia.org/wiki/Noble_gas] |
| | >>Note: The halogens or halogen elements are a series of nonmetal elements from Group 17 (old-style: VII or VIIA; Group 7 IUPAC Style) of the periodic table, comprising fluorine, F; chlorine, Cl; bromine, Br; iodine, I; and astatine, At. The undiscovered element 117, temporarily named ununseptium, may also be considered a halogen. |
| | The group of halogens is the only group which contains elements in all three familiar states of matter at standard temperature and pressure. |
| | [http://en.wikipedia.org/wiki/Halogen] |
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