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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 ...
Each chemical element has a unique atomic number (Z— for "Zahl", German for "number") representing the number of protons in its nucleus. [4] Each distinct atomic number therefore corresponds to a class of atom: these classes are called the chemical elements. [5] The chemical elements are what the periodic table classifies and organizes.
Heterocysts or heterocytes are specialized nitrogen-fixing cells formed during nitrogen starvation by some filamentous cyanobacteria, such as Nostoc, Cylindrospermum, and Anabaena. [1] They fix nitrogen from dinitrogen (N 2 ) in the air using the enzyme nitrogenase , in order to provide the cells in the filament with nitrogen for biosynthesis.
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.
The following table gives the crystalline structure of the most thermodynamically stable form(s) for elements that are solid at standard temperature and pressure. Each element is shaded by a color representing its respective Bravais lattice, except that all orthorhombic lattices are grouped together.
Here [Ne] refers to the core electrons which are the same as for the element neon (Ne), the last noble gas before phosphorus in the periodic table. The valence electrons (here 3s 2 3p 3) are written explicitly for all atoms. Electron configurations of elements beyond hassium (element 108) have never been measured; predictions are used below.
A period on the periodic table is a row of chemical elements. All elements in a row have the same number of electron shells. Each next element in a period has one more proton and is less metallic than its predecessor. Arranged this way, elements in the same group (column) have similar chemical and physical properties, reflecting the periodic law.
Superactinides – Hypothetical series of elements 121 to 157, which includes a predicted "g-block" of the periodic table. Transactinide elements – Elements after the actinides (atomic number greater than 103). Transplutonium elements – Elements with atomic number greater than 94. Transuranium elements – Elements with atomic number ...