The lightest chemical elements are hydrogen and helium, both created by Big Bang nucleosynthesis during the first 20 minutes of the universe in a ratioof around 3:1 by mass (or 12:1 by number of atoms), along with tiny traces of

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The various chemical elements are formally identified by their unique atomic numbers, by their accepted names, and by their symbols.
Atomic numbers
The known elements have atomic numbers from 1 through

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Only about 4% of the total mass of the universe is made of atoms or ions, and thus represented by chemical elements. This fraction is about 15% of the total matter, with the remainder of the matter (85%) being dark matter. The nature of dark matter is unknown,

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Evolving definitions
The concept of an "element" as an undivisible substance has developed through three major

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The following sortable table shows the 118 known chemical elements.
• Atomic number, Element, and Symbol all serve independently as

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• Biological roles of the elements
• Chemical database
• Discovery of the chemical elements

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The following graph (note log scale) shows the abundance of elements in our Solar System. The table shows the twelve most common elements in our galaxy (estimated

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