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
Phys.org - latest science and technology news stories Phys.org internet news portal provides the latest news on science including: Physics, Nanotechnology, Life Sciences, Space Science, Earth Science, Environment, Health and Medicine.
What does a chemical do? Addressing...
on November 15, 2018 at 3:00 pm
When I introduce myself as a Ph.D. student in chemistry, I can often spot fear and incomprehension in people's eyes: chemists are often pictured as crazy scientists, like Dr. Maru in Wonder Woman, doing black magic and explosions. It appears that most of the public fears are based on misunderstandings of the science. […]
Partial mycoheterotrophs: The green plants that...
on November 14, 2018 at 2:50 pm
You probably learned this basic lesson of biology in elementary school: Plants are self-feeders. These so-called autotrophs use the sun's energy and water to turn carbon dioxide from the air into food through the process known as photosynthesis. Autotrophic organisms sit at the base of every food chain on Earth and sustain all levels of life as we know it. […]
X-rays show how periods of stress changed an ice...
on November 14, 2018 at 1:09 pm
A few hundred thousand years ago during Earth's most recent ice age, a beefy subspecies of spotted hyena that was more than double the weight of its modern relative roamed Eurasia's snow-glazed terrain. Until their extinction about 11,000 years ago, these animals, now known as cave hyenas, would drag their prey into dens and devour them with bone-crushing jaws. […]
Pilot-scale plant to extract rare earth elements...
on November 8, 2018 at 2:00 pm
Americans use rare earth elements (REEs) every day—without knowing it. In fact, they are crucial to society. Rick Honaker, professor of mining engineering at the University of Kentucky, knows all about these fascinating elements and the modern electronics they make possible. […]
Shortening the rare-earth supply chain via...
on November 5, 2018 at 1:39 pm
Modern technology depends on a set of 17 elements at the foot of the periodic table. Known as rare earths (REs), many of these metals are highly magnetic, and find use in computing, green power and other technologies. However, because of rising prices, legal issues and the difficulty of mining, safeguarding their supply is a major scientific and political challenge. […]