A chemical element (sometimes called simply
element) is a unique type
of
atom characterized by the number of
protons in its nucleus. In
the bulk phase, a pure element consists of only one kind of atom. Atoms of the same element whose nuclei contain a different number of
neutrons are said to be different
isotopes of the element. A pure element can sometimes exist in different arrangements. These are called
allotropes. Chemical elements are commonly arranged in the
periodic table.
The official names of the chemical elements are decided by the International Union of Pure and Applied Chemistry.
Chemicals that are not elements are called compounds?. These include water, metal alloys, salts, oxides, and organic compounds.
See also discovery of the chemical elements
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