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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 ...
Hydrogen is the element with atomic number 1; helium, atomic number 2; lithium, atomic number 3; and so on. Each of these names can be further abbreviated by a one- or two-letter chemical symbol; those for hydrogen, helium, and lithium are respectively H, He, and Li. [6] Neutrons do not affect the atom's chemical identity, but do affect its weight.
An atom (or ion) whose oxidation number increases in a redox reaction is said to be oxidized (and is called a reducing agent). It is accomplished by loss of one or more electrons. The atom whose oxidation number decreases gains (receives) one or more electrons and is said to be reduced. This relation can be remembered by the following mnemonics.
The table is color-coded to show the chemical groupings. Small symbols pack in additional information: solid/liquid/gas, the color of an element, common in the human body, common in the earth's crust, magnetic metals, noble metals, radioactive, and rare or never found in nature.
This is an accepted version of this page This is the latest accepted revision, reviewed on 6 March 2025. For other color lists, see Lists of colors. This article relies largely or entirely on a single source. Relevant discussion may be found on the talk page. Please help improve this article by introducing citations to additional sources. Find sources: "List of colors" alphabetical – news ...
The list starts with 🜚 for gold and has early conventions that would later change: here ☿ is tin and ♃ electrum; ☾ is silver but ☽ is mercury. Many of the 'symbols' are simply abbreviations of the Greek word or phrase. View the files on Commons for the list of symbols. [citation needed]
A homocycle or homocyclic ring is a ring in which all atoms are of the same chemical element. [1] A heterocycle or heterocyclic ring is a ring containing atoms of at least two different elements, i.e. a non-homocyclic ring. [2] A carbocycle or carbocyclic ring is a homocyclic ring in which all of the atoms are carbon. [3]
The s-block is shifted up one row, thus all elements not in the s-block are now one row lower than in the standard table. For example, most of the fourth row in the standard table is the fifth row in this table. Helium is placed in group 2 (not in group 18). The elements remain positioned in order of atomic number (Z).