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Periodic table

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An important breakthrough in making sense of the list of known chemical elements (as well as in understanding the internal structure of atoms) was Dmitri Mendeleev's development of the first modern periodic table, or the periodic classification of the elements.

Mendeleev, a Russian chemist, felt that there was some type of order to the elements and he spent more than thirteen years of his life collecting data and assembling the concept, initially with the idea of resolving some of the disorder in the field for his students. Mendeleev found that, when the known chemical elements were arranged in order of increasing atomic weight, the resulting table displayed a recurring pattern, or periodicity, of properties within groups of elements. Mendeleev's law allowed him to build up a systematic periodic table of all the 66 elements then known based on atomic mass, which he published in Principles of Chemistry in 1869. His first Periodic Table was compiled on the basis of arranging the elements in ascending order of atomic weight and grouping them by similarity of properties.

Mendeleev had such faith in the validity of the periodic law that he proposed changes to the generally accepted values for the atomic weight of a few elements and, in his version of the periodic table of 1871, predicted the locations within the table of unknown elements together with their properties. He even predicted the likely properties of three yet-to-be-discovered elements, which he called ekaboron (Eb), ekaaluminium (Ea), and ekasilicon (Es), which proved to be good predictors of the properties of scandium, gallium, and germanium, respectively, which each fill the spot in the periodic table assigned by Mendeleev.

At first the periodic system did not raise interest among chemists.

However, with the discovery of the predicted elements, notably gallium in 1875, scandium in 1879, and germanium in 1886, it began to win wide acceptance. The subsequent proof of many of his predictions within his lifetime brought fame to Mendeleev as the founder of the periodic law. This organization surpassed earlier attempts at classification by Alexandre-Émile Béguyer de Chancourtois, who published the telluric helix, an early, three-dimensional version of the periodic table of the elements in 1862, John Newlands, who proposed the law of octaves (a precursor to the periodic law) in 1864, and Lothar Meyer, who developed an early version of the periodic table with 28 elements organized by valence in 1864. Mendeleev's table did not include any of the noble gases, however, which had not yet been discovered. Gradually the periodic law and table became the framework for a great part of chemical theory. By the time Mendeleyev died in 1907, he enjoyed international recognition and had received distinctions and awards from many countries.

In 1873, Jacobus Henricus van 't Hoff and Joseph Achille Le Bel, working independently, developed a model of chemical bonding that explained the chirality experiments of Pasteur and provided a physical cause for optical activity in chiral compounds. Van 't Hoff's publication, called Voorstel tot Uitbreiding der Tegenwoordige in de Scheikunde gebruikte Structuurformules in de Ruimte, etc. (Proposal for the development of 3-dimensional chemical structural formulae) and consisting of twelve pages text and one page diagrams, gave the impetus to the development of stereochemistry. The concept of the "asymmetrical carbon atom", dealt with in this publication, supplied an explanation of the occurrence of numerous isomers, inexplicable by means of the then current structural formulae. At the same time he pointed out the existence of relationship between optical activity and the presence of an asymmetrical carbon atom.

The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number (number of protons in the nucleus), electron configurations, and recurring chemical properties. The table also shows four rectangular blocks: s-, p- d- and f-block. In general, within one row (period) the elements are metals on the lefthand side, and non-metals on the righthand side.

The rows of the table are called periods; the columns are called groups. Six groups (columns) have names as well as numbers: for example, group 17 elements are the halogens; and group 18, the noble gases.

The periodic table can be used to derive relationships between the properties of the elements, and predict the properties of new elements yet to be discovered or synthesized. The periodic table provides a useful framework for analyzing chemical behavior, and is widely used in chemistry and other sciences.

Although precursors exist, Dmitri Mendeleev is generally credited with the publication, in 1869, of the first widely recognized periodic table. He developed his table to illustrate periodic trends in the properties of the then-known elements. Mendeleev also predicted some properties of then-unknown elements that would be expected to.

Periodic table. Modern periodic table, in 18-column layout (color legend below) The rows of the table are called periods; the columns are called groups. Six groups (columns) have names as well as numbers: for example, group 17 elements are the halogens; and group 18, the noble gases. The periodic table can be used to derive relationships between the properties of the elements, and predict the properties of new elements yet to be discovered or synthesized. The periodic table provides a useful framework for analyzing chemical behavior, and is widely used in chemistry and other sciences. Dmitri Mendeleev published in 1869 the first widely recognized periodic table. Overview Each chemical element has a unique atomic number representing the number of protons in its nucleus.

Dmitri Mendeleev

History. Overview. Grouping methods. Metals, Metalloids, and Non-metals. Periodic trends. History. Different periodic tables. Open questions and controversies. Isotopes. Allotropy. Diamond and graphite are two allotropes of carbon: pure forms of the same element that differ in crystalline structure.


For some elements, allotropes have different molecular formulae which can persist in different phases – for example, two allotropes of oxygen (dioxygen, O2, and ozone, O3), can both exist in the solid, liquid and gaseous states. Conversely, some elements do not maintain distinct allotropes in different phases – for example phosphorus has numerous solid allotropes, which all revert to the same P4 form when melted to the liquid state. History[edit] Differences in properties of an element's allotropes[edit] List of allotropes[edit] Typically, elements capable of variable coordination number and/or oxidation states tend to exhibit greater numbers of allotropic forms. Examples of allotropes include: [edit] [edit] [edit] Lanthanides and actinides[edit]

This is the first look at what happens to uranium fuel during a nuclear meltdown. Image: Corium lavas.

This is the first look at what happens to uranium fuel during a nuclear meltdown

Credit: U.S. Department of Energy via ABC Science By Fiona MacDonald A team of researchers in the US has performed a world-first experiment that will help them work out how uranium dioxide fuel behaves in its molten state – something that generally only occurs at the start of a nuclear meltdown. Hardnesses of the elements (data page) Chemical element. Elements and atoms. List of elements. From Wikipedia, the free encyclopedia The following is a list of the 118 identified chemical elements.

List of elements

List[edit] Notes[edit] ^1 The element does not have any stable nuclides, and a value in brackets, e.g. [209], indicates the mass number of the longest-lived isotope of the element. References[edit] Wieser, Michael E.; et al. (2013). External links[edit] The Elements Revealed: An Interactive Periodic Table. In the October 2011 issue of Scientific American, we celebrate the International Year of Chemistry.

Learn more about its impact on our daily lives in our Special Report. UPDATED: 06/18/2013 In honor of the 2013 Lindau meeting, which focuses on chemistry, we have updated our interactive periodic table with links to Nature Chemistry's In Your Element essay series. Each essay tells the story of a particular element, often describing its discovery, history and eventual uses. Main Sources & More to Explore: The Poisoner’s Handbook: Murder and the Birth of Forensic Medicine in Jazz Age New York. Interactive by Krista Fuentes. The NEW periodic table song. Who said music can't be educational?

The NEW periodic table song

AsapSCIENCE did a few versions of the Periodic Table Song before, and it's another physics tour de force. Set to Offenbach's Can-Can, a tune any Looney Tunes fan will be familiar with, the guys take you through the entire periodic table, wasting no time other than to give a few short comments about some of the elements. It's highly enjoyable. You can get it here on iTunes, and there are more download links if you click through to the video.

The Comic Book Periodic Table of the Elements. The Elements Revealed: An Interactive Periodic Table. 2016 January 25 - Where Your Elements Came From. Discover the cosmos!

2016 January 25 - Where Your Elements Came From

Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2016 January 25. Abundance of the chemical elements. For example, the abundance of oxygen in pure water can be measured in two ways: the mass fraction is about 89%, because that is the fraction of water's mass which is oxygen.

Abundance of the chemical elements

However, the mole-fraction is 33.3333...% because only 1 atom of 3 in water, H2O, is oxygen. As another example, looking at the mass-fraction abundance of hydrogen and helium in both the Universe as a whole and in the atmospheres of gas-giant planets such as Jupiter, it is 74% for hydrogen and 23-25% for helium; while the (atomic) mole-fraction for hydrogen is 92%, and for helium is 8%, in these environments. Timeline of chemical element discoveries. The discovery of the 118 elements known to exist today is presented here in chronological order.

Timeline of chemical element discoveries

The elements are listed generally in the order in which each was first defined as the pure element, as the exact date of discovery of most elements cannot be accurately defined. Given is each element's name, atomic number, year of first report, name of the discoverer, and some notes related to the discovery. Table[edit] Unrecorded discoveries[edit] Recorded discoveries[edit] Graphics[edit] See also[edit] References[edit] External links[edit] Four new element names are on the table. Time to throw out that old copy of the periodic table: New names have just been penciled in for four elements officially recognized back in December.

Four new element names are on the table

Nihonium, moscovium, tennessine, and oganesson will grace the blocks assigned to atomic numbers 113, 115, 117, and 118, said the International Union of Pure and Applied Chemistry (IUPAC) today. Barring any serious challenges during a 5-month public comment period that ends in November, the new names will be officially added to the table (above). Nihonium, discovered by a Japanese team, means “the land of the rising sun,” while moscovium and tennessine are named after places near the labs where they were discovered (Moscow and Tennessee, of course). And oganesson recognizes the work of Russian chemist Yuri Oganessian. By tradition, the right to suggest a name for an element is granted to its discoverer, although IUPAC has the final say.

Nucleosynthesis. Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons, primarily protons and neutrons.


The first nuclei were formed about three minutes after the Big Bang, through the process called Big Bang nucleosynthesis. It was then that hydrogen and helium formed to become the content of the first stars, and this primeval process is responsible for the present hydrogen/helium ratio of the cosmos. With the formation of stars, heavier nuclei were created from hydrogen and helium by stellar nucleosynthesis, a process that continues today. Some of these elements, particularly those lighter than iron, continue to be delivered to the interstellar medium when low mass stars eject their outer envelope before they collapse to form white dwarfs.

The remains of their ejected mass form the planetary nebulae observable throughout our galaxy. Timeline[edit]

Periodic tables