Chemical element
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A chemical element or simply element, is a species of atoms having the same number of protons in their atomic nuclei (or the same atomic number, Z).
General aspects
Chemical elements constitute all of the observable matter of the universe.
118 elements are identified, of which the first 94 occur naturally on Earth with the remaining 24 being synthetic elements. There are 80 elements that have at least one stable isotope and 38 that have exclusively radionuclides, which decay over time into other elements.
The properties of the chemical elements are summarized in the periodic table, which organizes the elements by increasing atomic number into rows ("periods") in which the columns ("groups") share recurring ("periodic") physical and chemical properties.
