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[L. elementum, a rudiment]
In chemistry, a pure substance consisting of only one type of atom. Further breakdown by nonchemical means of an element results in subatomic particles (protons, neutrons and electrons), which are indistinguishable from those from other elements. Elements exist in free and combined states. There are 110 named elements and others yet to be fully characterized and named.
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Oxygen, carbon, hydrogen, nitrogen, phosphorus, and sulfur are found in all living organisms. These six elements and calcium make up 99% of the human body mass. Sodium, potassium, magnesium, chlorine, iodine, and iron form 0.9% of the body mass.

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