The molecular structure of a substance is described by the combination of nuclei and electrons that comprise its constitute molecules. This includes the molecular geometry

Molecular geometry

Molecular geometry or molecular structure is the three-dimensional arrangement of the atoms that constitute a molecule. It determines several properties of a substance including its reactivity, polarity, phase of matter, color, magnetism, and biological activity.- Molecular geometry determination...

 (essentially the arrangement, in space, of the equilibrium positions of the constituent atoms -- in reality, these are in a state of constant vibration, at temperatures above absolute zero), the electronic properties of the bonds, and further molecular properties. The determination of molecular structure uses a multitude of experimental methods, that include X-ray diffraction, electron diffraction

Electron diffraction

Electron diffraction refers to the wave nature of electrons. However, from a technical or practical point of view, it may be regarded as a technique used to study matter by firing electrons at a sample and observing the resulting interference pattern...

, many kinds of optical spectroscopy, nuclear magnetic resonance

Nuclear magnetic resonance

Nuclear magnetic resonance is a physical phenomenon in which magnetic nuclei in a magnetic field absorb and re-emit electromagnetic radiation...

, electron spin resonance, and mass spectrometry

Mass spectrometry

Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of charged particles.It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical structures of molecules, such as peptides and...

. The prediction and explanation of molecular structure uses quantum theory of valency and methods of molecular modeling. The term "molecular structure" extends to multi-molecular complexes.