Chemical composition (source code)

= Chemical composition
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<Chemical composition> specifies which chemical components or elements a material contains and in what proportions. The description can use atom ratios, formula units, mole fractions, or mass fractions, depending on the question.

Composition is distinct from spatial structure. Two carbon allotropes can share elemental composition but differ in bonding, while two mixtures containing the same components can differ in their component fractions and physical behavior.