Chemical element

There are now 118 known elements. The first 94 occur naturally on Earth, and the remaining 24 are synthetic elements produced in nuclear reactions. Save for unstable radioactive elements which decay quickly, nearly all of the elements are available industrially in varying amounts.

About Chemical element in brief

There are now 118 known elements. The first 94 occur naturally on Earth, and the remaining 24 are synthetic elements produced in nuclear reactions. Save for unstable radioactive elements which decay quickly, nearly all of the elements are available industrially in varying amounts. The discovery and synthesis of further new elements is an ongoing area of scientific study. The lightest chemical elements are hydrogen and helium, both created by Big Bang nucleosynthesis during the first 20 minutes of the universe in a ratio of around 3: 1 by mass. The very heaviest elements undergo radioactive decay with half-lives so short that they are not found in nature and must be synthesized. Six of these occur in extreme trace quantities: technetium, promethium, and plutonium. The remaining 24, not found today, have been artificially produced in astronomical spectra or in supernovae, where short-lived radioactive elements are being made. These elements have been detected in the spectra of stars at large, large, and small distances from Earth. All of the baryonic matter in the universe is composed of chemical elements. When different elements undergo chemical reactions, atoms are rearranged into new compounds held together by chemical bonds. Only a minority of elements, such as silver and gold, are found uncombined as relatively pure native element minerals. On Earth, small amounts of new atoms are naturally produced in nucleogenic reactions, or in cosmogenic processes such as cosmic ray spallation. New atoms are also naturally produced on Earth as radiogenic daughter isotopes of ongoing radioactive decay processes like alpha decay, beta decay, spontaneous fission, cluster decay, and other rarer modes of decay.

Of the 94 naturally occurring elements, those with atomic numbers 1 through 82 each have at least one stable isotope. Isotopes considered stable are those for which no radioactive decay has yet been observed. At over 1.9×1019 years, over a billion times longer than the current estimated age of the Universe, bismuth-209 has the longest known alpha decay half-life of any naturally occurring element, and is almost always considered on par with the 80 stable elements. Most recently, the synthesis of element 118 was reported in October 2006. These elements are present from the formation of the solar system, or artificially produced from primordial nuclides present in the primordial solar system or from the supernova formation of primordial primordial stars. In this context, ‘known’ means observed well enough, even from just a few decay products, to have been differentiated from other elements. In this case, the word ‘element’ is used to refer to elements that have been observed in some way by chemists to have a certain chemical or physical property that can be distinguished from those that have not been observed by scientists. By November 2016, the International Union of Pure and Applied Chemistry had recognized a total of 118 elements. Of these 118 elements, 94 of them are naturally occurring on Earth.

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