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A molecule is formed from two or more atoms of a single element. An example is h2o. two hydrogen atoms and one oxygen atom forming a molecule of water! This question is archived.
An element is a substance composed of identical atoms. This definition was one of the cornerstones of John Dalton's atomic theory, but it too was made obsolete by the discovery of isotopes.Atoms of the same element have different numbers of neutrons in their nuclei.n other words, all atoms of an element have the same atomic number. This modern definition resolves some sticky situations encountered with older definitions: The definition above doesn't make element and mixture mutually exclusive classifications of matter.