Molecular structure

Molecular structure is the arrangement of atoms and chemical bonds within a molecule. It includes connectivity and the molecule’s three-dimensional shape.

Chemical bond: An attractive interaction that holds atoms or ions together in a chemical substance. Bonds define which atoms are connected and constrain their relative positions.
X-ray crystallography: A method that uses X-ray diffraction by crystals to determine the arrangement of atoms in a structure. It can reveal precise atomic positions in crystalline molecular solids.
Structure–activity relationship: A relationship between a compound’s chemical structure and its biological activity or other measured effect. Small structural changes can alter a molecule’s potency, selectivity, or toxicity.
Structural formula: A representation showing how atoms in a molecule are connected by chemical bonds. It records connectivity, but usually does not specify one three-dimensional conformation.
Chemical reactivity: The tendency of a substance to undergo chemical reactions under specified conditions. Bonding and electron distribution help determine which reactions a molecule undergoes.
Molecular geometry: The three-dimensional arrangement of atoms in a molecule, excluding lone-pair positions. It describes the shape produced by a molecule’s atom connectivity and bonding.
Nuclear magnetic resonance spectroscopy: A technique that uses nuclear spin behavior in magnetic fields to probe molecular environments and dynamics. Chemical shifts and couplings provide evidence about molecular connectivity and conformation.
Drug design: The process of creating or optimizing compounds to interact with biological targets for therapeutic effect. Molecular shape and chemical features guide how candidate drugs bind targets.
Molecular formula: A notation stating the kinds and numbers of atoms in a molecule. It gives composition but cannot distinguish most different molecular structures.
Dipole moment: A vector measure of the separation of positive and negative charge in a system. Molecular geometry determines whether individual bond dipoles combine or cancel.

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