periodic table of the chemical elements

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 January 27, 2008 (while element 118 has been synthesized, element 117 has not).

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. The Wide Periodic Table incorporates the f-block; the Extended Periodic Table incorporates the f-block and adds the theoretical g-block.

Element categories in the periodic table Metals Metalloids Nonmetals 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	Borders show natural occurrence Primordial From decay Synthetic Undiscovered

http://en.wikipedia.org/wiki/Periodic_table

Periodic Table

Periodic Table first discovered in 1869 by Dmitry I. Mendeleyev is a way of presenting all the elements so as to show their similarities and differences. The elements are arranged in increasing order of atomic number(Z) as you go from left to right accross the table. The horizontal rows a called periods and the vertical rows, groups.

A noble gas is found at the right hand side of each period. There is a progression from metals to non-metals across each period. Elements found in groups (e.g. alkali, halogens) have a similar electronic configuration. The number of electrons in outer shell is the same as the number of the group (e.g. lithium 2·1).

The block of elements between groups II and III are called transition metals. These are similar in many ways; they produce colored compounds, have variable valency and are often used as catalysts. Elements 58 to 71 are known as lanthanide or rare earth elements. These elements are found on earth in only very small amounts.

Elements 90 to 103 are known as the actinide elements. They include most of the will known elements which are found in nuclear reactions. The elements with larger atomic numbers than 92 do not occur naturally. They have all been produced artificially by bombarding other elements with particles.

http://www.chemicool.com/

What is the Periodic Table of The Elements?

"It is a huge, efficient resource!"

The periodic table is the most important chemistry reference there is. It arranges all the known elements in an informative array. Elements are arranged left to right and top to bottom in order of increasing atomic number. Order generally coincides with increasing atomic mass.

The different rows of elements are called periods. The period number of an element signifies the highest energy level an electron in that element occupies (in the unexcited state). The number of electrons in a period increases as one traverses down the periodic table; therefore, as the energy level of the atom increases, the number of energy sub-levels per energy level increases.

Using the data in the table scientists, students, and others that are familiar with the periodic table can extract information concerning individual elements. For instance, a scientist can use carbon's atomic mass to determine how many carbon atoms there are in a 1 kilogram block of carbon.

People also gain information from the periodic table by looking at how it is put together. By examining an element's position on the periodic table, one can infer the electron configuration. Elements that lie in the same column on the periodic table (called a "group") have identical valance electron configurations and consequently behave in a similar fashion chemically. For instance, all the group 18 elements are inert gases. The periodic table contains an enormous amount of important information. People familiar with how the table is put together can quickly determine a significant amount of information about an element, even if they have never heard of it.

http://periodic.lanl.gov/what.htm

History of the periodic table of chemical elements

In 1669 German merchant and amateur alchemist Hennig Brand attempted to created a Philosopher’s Stone; an object that supposedly could turn metals into pure gold. He heated residues from boiled urine, and a liquid dropped out and burst into flames. This was the first discovery of phosphorus.

In 1680 Robert Boyle also discovered phosphorus, and it became public.

In 1809 at least 47 elements were discovered, and scientists began to see patterns in the characteristics.

In 1863 English chemist John Newlands divided the than discovered 56 elements into 11 groups, based on characteristics.

In 1869 Russian chemist Dimitri Mendeleev started the development of the periodic table, arranging chemical elements by atomic mass. He predicted the discovery of other elements, and left spaces open in his periodic table for them.

In 1886 French physicist Antoine Bequerel first discovered radioactivity. Thomson student from New Zealand Ernest Rutherford named three types of radiation; alpha, beta and gamma rays. Marie and Pierre Curie started working on the radiation of uranium and thorium, and subsequently discovered radium and polonium. They discovered that beta particles were negatively charged.

In 1894 Sir William Ramsay and Lord Rayleigh discovered the noble gases, which were added to the periodic table as group 0.

In 1897 English physicist J. J. Thomson first discovered electrons; small negatively charged particles in an atom. John Townsend and Robert Millikan determined their exact charge and mass.

In 1900 Bequerel discovered that electrons and beta particles as identified by the Curies are the same thing.

In 1903 Rutherford announced that radioactivity is caused by the breakdown of atoms.

In 1911 Rutherford and German physicist Hans Geiger discovered that electrons orbit the nucleus of an atom.

In 1913 Bohr discovered that electrons move around a nucleus in discrete energy called orbitals. Radiation is emitted during movement from one orbital to another.

In 1914 Rutherford first identified protons in the atomic nucleus. He also transmutated a nitrogen atom into an oxygen atom for the first time. English physicist Henry Moseley provided atomic numbers, based on the number of electrons in an atom, rather than based on atomic mass.

In 1932 James Chadwick first discovered neutrons, and isotopes were identified. This was the complete basis for the periodic table. In that same year Englishman Cockroft and the Irishman Walton first split an atom by bombarding lithium in a particle accelerator, changing it to two helium nuclei.

In 1945 Glenn Seaborg identified lanthanides and actinides (atomic number >92), which are usually placed below the periodic table.

http://www.lenntech.com/Periodic-chart-elements/history-periodic-table.htm

WebElements periodic table

The periodic "law" of chemistry recognises that many properties of the chemical elements are periodic functions of their atomic number (the number of protons within the element's atomic nucleus). The periodic table is an arrangement of the chemical elements ordered by atomic number in columns (groups) and rows (periods) presented so as to emphasize their periodic properties.

The element polonium is very much in the news at present, perhaps for the first time ever, and for the wrong reasons. This site does contain further information about polonium.

The groups (columns in the periodic table) are numbered 1-18. Some groups enjoy non-systematic names as well. The include Group 1 (alkali metals), Group 2 (alkaline earth metals), Group 15 (pnictogens, or pnicogens), Group 16 (chalcogens), Group 17 (halogens) and Group 18 (noble gases). While not groups in the periodic table, some other groupings of elements are often named as well. These include the lanthanoids (less preferably lanthanides) and actinoids (less preferably actinides).

There are many different ways, sometimes ingenious, of arranging the chemical elements according to which properties are of particular interest but that shown here is a standard form of the periodic table. The relative merits of various other periodic table organisations is still the subject of debate. Particularly useful versions include the following:

• Extended periodic table
• Janet periodic table
• Mendeleev's original periodic table

While the name Dmitri Mendeleev is usually credited with the with the form of periodic table as we know it today, many other excellent researchers made profound contributions to its development, including Antoine Lavoisier, Jöns Jakob Berzelius, Johann Döbereiner, John Newlands, Alexandre-Émile Béguyer de Chancourtois, Lothar Meyer, and others.

http://www.webelements.com/

Chimei Model: DTL-752E600

Features:

• High Resolution: 1920 x 1080
• High Brightness: 500cd/m²
• High Contrast: 1500:1
• Fast Response Time: 6.5ms
• Wide Screen Format: 16:9
• Wide Viewing Angles: 176° (H) / 176° (V)
• Wide Color Gamut (WCG)
• Stylish Design, Glass Stand

TV Model Name here (e.g. T3715C)
	Display	Screen Size	1152 (H) x 648 (V) mm ( 52.037” diagonal )
		Aspect Ratio	16:9
		Panel Resolution	1920 x 1080
		Brightness	500 cd/m2
		Contrast Ratio (typ.)	1500 : 1
		Viewing Angle	176O (H) x 176O (V)
		Response Time	6. 5ms
	Picture	Picture Mode	User / Movie / Game / Vivid / Sport
	Sound	Speaker Output	15W x 2 (SRS TruSurround XT )
	Features	HDMI	Yes
		Aspect Ratio	Auto / Normal / Full / Zoom 1/ Zoom 2 / Panorama
		PIP Function	Yes
		Sleep Timer	Off / 15 / 30 / 60 / 90 / 120 min
		Supported Scanning Format	480i / 480p / 576i / 576p / 720p / 1080i / 1080p
		Teletext	1000 pages
		Noise Reduction	Yes
	Connections	HDMI	2
		Component (Y-Pb-Pr)	Yes
		SCART 1 - CVBS/S-RGB(In) TV (Out)	Yes
		SCART 2 - CVBS (In) AV/TV (Out)	Yes
		S-Video In	Via Scart
		Audio R/L In	Yes
		PC-VGA	Yes
		Earphone Output	Yes
	Power	Supply	AC 100-240V, 4. 5A, 50/60Hz
		Consumption	Operations <380w
		Stand-by	<1w
	Dimensions	TV	1294 (W) x 843(H) x 120 (T) mm
		Carton	1420 (W) x 1000 (H) x 255 (T)
	Weight	Net	34. 5 Kg
		Gross	40. 5Kg
	Vesa Mounting	Mounting Kit	400 x 200 mm
	Special Feature	Wide Color Gamut (WCG)

http://www.chimei.com.sg/default.aspx?pageId=269

LCD TV vs. Plasma PICTURE CONSIDERATIONS

CONTRAST / BLACK LEVELS

Plasma technology has certainly achieved quite high contrast ratios, a measure of the blackest black compared to the whitest white. Many plasma display manufacturers boast a contrast ratio of 3000:1 these days though our tests have not proven these numbers out. Panasonic has long been the leader in plasma black levels and we measure contrast of a 42" HD Panasonic plasma at about ANSI 1450:1 - still impressive. Plasma displays achieve such impressive black levels by using internal algorithms to block the power to particular pixels in order to render a pixel "dark" or black. While this can limit a plasma television's gray scaling, it does produce exceptionally black blacks - depending on the manufactured plasma display element (i.e. glass). A plasma TV uses the most power when it is producing full white. As a result, some 2nd tier manufactured brands of plasma TVs have an audible buzz or whining sound when displaying white or very light images.

LCD (liquid crystal diode) displays, by contrast, utilize electric charges to twist and untwist liquid crystals, which causes them to block light and, hence, emit blacks. The higher the voltage passing through the liquid crystals in a given pixel, the more fully those crystals untwist and effectively block light - all of which makes these pixels darker. As opposed to plasma, LCD TVs use the most power when displaying a very dark or black image. This is a difficult process, and despite recent improvements in LCD black levels, only the best LCD televisions (like those produced by Sharp and Sony) have managed to topple the 1000:1 contrast ratio barrier. Recent improvements have brought LCD displays up to the level of plasma. The one continual drawback here for LCD is off axis viewing, when black levels consistently drop.

ADVANTAGE: Closer than a year ago, but still Plasma. LCD TV manufacturers have made great improvements in black levels and in many cases have managed to match the contrast ratio of plasma displays. However, Plasma displays still maintain a clear advantage in this category due to fading blacks when viewing LCDs from off axis. For scenes with a lot of dark and light images shown simultaneously - as with content originating from DVDs, video games, and NTSC TV signals - plasmas still consistently outperform LCD TVs.

http://www.lcdtvbuyingguide.com/lcdtv-plasmavslcd.shtml

LCD Technology

LCD technology is based on the properties of polarized light. Two thin, polarized panels sandwich a thin liquid-crystal gel that is divided into individual pixels. An X/Y grid of wires allows each pixel in the array to be activated individually. When an LCD pixel darkens, it polarizes at 90 degrees to the polarizing screens.

This pixel has darkened. The pixel darkens in proportion to the voltage applied to it: for a bright detail, a low voltage is applied to the pixel; for a dark shadow area, a higher voltage is applied. LCDs are not completely opaque to light, however; some light will always go through even the blackest LCD pixels.

Developments in LCD televisions

TVs based on PVA and S-PVA LCD panels deliver a broad viewing angle, up to 178 degrees. They also deliver an adequate contrast ratio for viewing bright scenes, as well as dark scenes in bright rooms. The dynamic contrast technique improves contrast when viewing dark scenes in a dark room. Alternatively, some manufacturers produce LCD TVs that throw light on the wall behind it to help make dark scenes look darker. PVA and S-PVA panels generally have difficulty with ghosting when going between different shades of dark colours, however in new televisions this is compensated to some degree using a technique called overdriving.

Moving pictures on a CRT TV do not exhibit any sort of "ghosting" because the CRT's phosphor, charged by the strike of electrons, emits most of the light in a very short time, under 1 ms, compared with the refresh period of e.g. 20 ms (for 50 fps video). In LCDs, each pixel emits light of set intensity for a full period of 20 ms (in this example), plus the time it takes for it to switch to the next state, typically 12 to 25 ms.

The second time (called the "response time") can be shortened by the panel design (for black-to-white transitions), and by using the technique called overdriving (for black-to-gray and gray-to-gray transitions); however this only can go down to as short as the refresh period.

This is usually enough for watching film-based material, where the refresh period is so long (1/24 s, or nearly 42 ms), and jitter is so strong on moving objects that film producers actually almost always try to keep object of interest immobile in the film's frame.

Video material, shot at 50 or 60 frames a second, actually tries to capture the motion. When the eye of a viewer tracks a moving object in video, it doesn't jump to its next predicted position on the screen with every refresh cycle, but it moves smoothly; thus the TV must display the moving object in "correct" places for as long as possible, and erase it from outdated places as quickly as possible.

Although ghosting was a problem when LCD TVs were newer, the manufacturers have been able to shorten response time to 2ms on many computer monitors and around an average of 8 ms for TVs.

There are two emerging techniques to solve this problem. First, the backlight of the LCD panel may be fired during a shorter period of time than the refresh period, preferably as short as possible, and preferably when the pixel has already settled to the intended brightness. This technique resurrects the flicker problem of the CRTs, because the eye is able to sense flicker at the typical 50 or 60 Hz refresh rates.

Another approach is to double the refresh rate of the LCD panel, and reconstruct the intermediate frames using various motion compensation techniques, extensively tested on high-end "100 Hz" CRT televisions in Europe.

The best approach may be a combination of two, possibly allowing the viewer to switch them on or off when viewing video- or film-based material.

Some manufacturers are also experimenting with extending colour reproduction of LCD televisions. Although current LCD panels are able to deliver all sRGB colours using an appropriate combination of backlight's spectrum and optical filters, manufacturers want to display even more colours. One of the approaches is to use a fourth, or even fifth and sixth colour in the optical colour filter array. Another approach is to use two sets of suitably narrowband backlights (e.g. LEDs), with slightly differing colours, in combination with broadband optical filters in the panel, and alternating backlights each consecutive frame.

Fully using the extended colour gamut will naturally require an appropriately captured material and some modifications to the distribution channel. Otherwise, the only use of the extra colours would be to let the viewer boost the colour saturation of the TV picture beyond what was intended by the producer, but avoiding the otherwise unavoidable loss of detail ("burnout") in saturated areas.

http://en.wikipedia.org/wiki/Liquid_crystal_display_television