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A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
Periodic tables usually at least show the elements' symbols; many also provide supplementary information about the elements, either via colour-coding or as data in the cells. The above table shows the names and atomic numbers of the elements, and also their blocks, natural occurrences and standard atomic weights. For the short-lived elements ...
This is a list of chemical elements and their atomic properties, ordered by atomic number (Z). Since valence electrons are not clearly defined for the d-block and f-block elements, there not being a clear point at which further ionisation becomes unprofitable, a purely formal definition as number of electrons in the outermost shell has been used.
Radioactive isotope table "lists ALL radioactive nuclei with a half-life greater than 1000 years", incorporated in the list above. The NUBASE2020 evaluation of nuclear physics properties F.G. Kondev et al. 2021 Chinese Phys. C 45 030001. The PDF of this article lists the half-lives of all known radioactives nuclides.
This is an accepted version of this page This is the latest accepted revision, reviewed on 2 March 2025. Periodic table of the elements with eight or more periods Extended periodic table Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese ...
Selenium, which is an essential element for animals and prokaryotes and is a beneficial element for many plants, is the least-common of all the elements essential to life. [3] [63] Selenium acts as the catalytic center of several antioxidant enzymes, such as glutathione peroxidase, [11] and plays a wide variety of other biological roles.
Octal (base 8) is a numeral system with eight as the base.. In the decimal system, each place is a power of ten.For example: = + In the octal system, each place is a power of eight.
In chemistry, an octatomic element is an element that, at some standard temperature and pressure, is in a configuration of eight atoms bound together (a homonuclear molecule). The canonical example is sulfur, S 8, [1] but red selenium is also an octatomic element stable at room temperature. Octaoxygen is also known, but it is extremely unstable.