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How many molecules are in one mole of a substance?
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molecule
Several methods of representing a molecule's structure. In Lewis structures, element symbols represent atoms, and dots represent electrons surrounding them. A pair of shared electrons (covalent bond) may also be shown as a single dash. The ball-and-stick model better illustrates the spatial arrangement of the atoms. For aromatic compounds, the Kekulé structure is common, in which each bond is represented by a dash, carbon atoms are implied where two or more lines meet, and hydrogen atoms are usually omitted. Bond-line formulas, similar to the Kekulé structure, are often used for complex nonaromatic organic compounds. Sugars are often drawn as Fischer projections, in which the carbon “backbone” is drawn as a straight vertical line, with carbon atoms implied where horizontal lines intersect the vertical one.
In chemistry, one mole of any substance contains exactly units, such as molecules, atoms, or ions.12
This specific quantity is known as Avogadro’s number (or Avogadro’s constant), named in honor of the physicist Amedeo Avogadro. The General Conference on Weights and Measures established this fixed value for the International System of Units (SI) in 2019, ensuring that the number of particles in a mole remains consistent across all substances regardless of their individual mass.12