Periodic Table of Elements (International Union of Pure and Applied Chemistry)
Interactive Periodic Table of Elements (Los Alamos National Laboratory)
Periodic Table (American Chemical Society)
These are organized by a classification scheme developed exclusively for Cosma. More…
Periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties, whose structure shows periodic trends. Generally, within one row (period) the elements are metals to the left, and non-metals to the right, with the elements having similar chemical behaviours placed in the same column. Table rows are commonly called periods and columns are called groups. Six groups have accepted names as well as assigned numbers: for example, group 17 elements are the halogens; and group 18 are the noble gases. Also displayed are four simple rectangular areas or blocks associated with the filling of different atomic orbitals.
The organization of the periodic table can be used to derive relationships between the various element properties, but also the predicted chemical properties and behaviours of undiscovered or newly synthesized elements. Russian chemist Dmitri Mendeleev was the first to publish a recognizable periodic table in 1869, developed mainly to illustrate periodic trends of the then-known elements. He also predicted some properties of unidentified elements that were expected to fill gaps within the table. Most of his forecasts proved to be correct. Mendeleev’s idea has been slowly expanded and refined with the discovery or synthesis of further new elements and the development of new theoretical models to explain chemical behaviour. The modern periodic table now provides a useful framework for analyzing chemical reactions, and continues to be widely used in chemistry, nuclear physics and other sciences.
All the elements from atomic numbers 1 (hydrogen) through 118 (oganesson) have been either discovered or synthesized, completing the first seven rows of the periodic table. The first 98 elements exist in nature, although some are found only in trace amounts and others were synthesized in laboratories before being found in nature. Elements 99 to 118 have only been synthesized in laboratories or nuclear reactors. The synthesis of elements having higher atomic numbers is currently being pursued: these elements would begin an eighth row, and theoretical work has been done to suggest possible candidates for this extension. Numerous synthetic radionuclides of naturally occurring elements have also been produced in laboratories. — Wikipedia
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New scale for electronegativity rewrites the...
on January 17, 2019 at 12:43 pm
Electronegativity is one of the most well-known models for explaining why chemical reactions occur. Now, Martin Rahm from Chalmers University of Technology, Sweden, has redefined the concept with a new, more comprehensive scale. His work, undertaken with colleagues including a Nobel Prize-winner, has been published in the Journal of the American Chemical Society. […]
World's oldest periodic table chart found in St...
on January 17, 2019 at 11:32 am
A periodic table chart discovered at the University of St Andrews is thought to be the oldest in the world. […]
New technique more precisely determines the ages...
on January 10, 2019 at 9:00 pm
How old are each of the stars in our roughly 13-billion-year-old galaxy? A new technique for understanding the star-forming history of the Milky Way in unprecedented detail makes it possible to determine the ages of stars at least two times more precisely than conventional methods, Embry-Riddle Aeronautical University researchers reported Jan. 10 at the American Astronomical Society (AAS) meeting. […]
Phosphorus: 350 years after its discovery, this...
on January 10, 2019 at 2:20 pm
It's time to buy a lot of candles. And if we light them with matches, it will only be possible because of the anniversary in question. It's happy 350th birthday to the discovery of phosphorus, an element that is essential for life as we know it. […]
Greener hydrogen from water
on January 4, 2019 at 1:40 pm
The idea of using hydrogen as the basis of a clean sustainable energy source, often termed a hydrogen economy, has been a topic of conversation for decades. Hydrogen fuel, for example, doesn't emit any carbon dioxide and is considered more sustainable than traditional fossil fuels. […]