molekylformeln

Molekylformeln, or molecular formula, is a concise notation used in chemistry to specify the exact number of each type of atom in a discrete molecule. It uses element symbols and subscripts to indicate how many atoms of each element are present. For example, the molecular formula of water is H2O, showing two hydrogen atoms for every one oxygen atom. Glucose has the molecular formula C6H12O6, indicating a total of 24 atoms in a single molecule.

The molecular formula reveals composition but not the arrangement of atoms within the molecule. It differs from the empirical formula, which expresses the simplest whole-number ratio of elements in a compound (such as CH2O for the empirical formula of glucose). Some substances share the same empirical formula but have different molecular formulas, reflecting different structures or sizes.

Molecular formulas apply to discrete molecules, including covalent compounds, and, for certain ionic substances, to formula units when a well-defined molecule is not present. For example, sodium chloride is commonly written NaCl, describing a formula unit rather than a discrete molecule in the solid lattice.

Determination of the molecular formula can involve experimental data such as elemental analysis or high-resolution mass spectrometry, combined with knowledge of the compound’s composition and molar mass. The molecular formula, together with structural information when available, provides a complete description of a molecule’s identity.

Limitations arise for large polymers or biomolecules where a single molecular formula may be insufficient to describe the full structure or sequence, requiring additional descriptors to convey connectivity and arrangement.