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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 ...
Transition elements * Elements in groups 3 to 11 or 3 to 12 (the latter making up the d-block) Pnictogens: The elements of group 15: N, P, As, Sb, Bi † Chalcogens: The elements of group 16: O, S, Se, Te, Po † Halogens: The elements of group 17: F, Cl, Br, I, At † Noble gases: The elements of group 18: He, Ne, Ar, Kr, Xe, Rn †
Chemical symbols are the abbreviations used in chemistry, mainly for chemical elements; but also for functional groups, chemical compounds, and other entities. Element symbols for chemical elements, also known as atomic symbols , normally consist of one or two letters from the Latin alphabet and are written with the first letter capitalised.
The first letter is always capitalized. While the symbol is often a contraction of the element's name, it may sometimes not match the element's English name; for example, "Pb" for lead (from Latin plumbum) or "W" for tungsten (from German Wolfram). Elements which have only temporary systematic names are given temporary three-letter symbols (e.g ...
There are currently seven complete periods in the periodic table, comprising the 118 known elements. Any new elements will be placed into an eighth period; see extended periodic table. The elements are colour-coded below by their block: red for the s-block, yellow for the p-block, blue for the d-block, and green for the f-block.
Groups may also be identified using their topmost element, or have a specific name. For example, group 16 is also described as the "oxygen group" and as the " chalcogens ". An exception is the " iron group ", which usually refers to group 8 , but in chemistry may also mean iron , cobalt , and nickel , or some other set of elements with similar ...
Sodium is a chemical element; it has symbol Na (from Neo-Latin natrium) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable isotope is 23 Na. The free metal does not occur in nature and must be prepared from compounds.