Editing Molecule (section)

== Molecular geometry ==
{{Main|Molecular geometry}}

[[File:Cyanostar STM.png|thumb|left|upright|Structure and [[Scanning tunneling microscopy|STM]] image of a "cyanostar" [[dendrimer]] molecule.<ref>{{cite journal|doi=10.1039/C4CC03725A|pmid=25080328|title=Anion-induced dimerization of 5-fold symmetric cyanostars in 3D crystalline solids and 2D self-assembled crystals|journal=Chemical Communications|volume=50|issue=69|pages=9827–30|year=2014|last1=Hirsch|first1=Brandon E.|last2=Lee|first2=Semin|last3=Qiao|first3=Bo|last4=Chen|first4=Chun-Hsing|last5=McDonald|first5=Kevin P.|last6=Tait|first6=Steven L.|last7=Flood|first7=Amar H.|s2cid=12439952 |url=https://zenodo.org/record/889879|access-date=20 April 2018|archive-date=31 March 2021|archive-url=https://web.archive.org/web/20210331062049/https://zenodo.org/record/889879|url-status=live}}</ref>]]

Molecules have fixed [[mechanical equilibrium|equilibrium]] geometries—bond lengths and angles— about which they continuously oscillate through vibrational and rotational motions. A pure substance is composed of molecules with the same average geometrical structure. The chemical formula and the structure of a molecule are the two important factors that determine its properties, particularly its [[reactivity (chemistry)|reactivity]]. [[Isomers]] share a chemical formula but normally have very different properties because of their different structures. [[Stereoisomer]]s, a particular type of isomer, may have very similar physico-chemical properties and at the same time different [[biochemistry|biochemical]] activities.