section_path: Molecular size
section_name: Molecular size
paragraph_text: Molecular size
  
  Most molecules are far too small to be seen with the naked eye, although molecules of many polymers can reach macroscopic sizes, including biopolymers such as DNA. Molecules commonly used as building blocks for organic synthesis have a dimension of a few angstroms (Å) to several dozen Å, or around one billionth of a meter. Single molecules cannot usually be observed by light (as noted above), but small molecules and even the outlines of individual atoms may be traced in some circumstances by use of an atomic force microscope. Some of the largest molecules are macromolecules or supermolecules.
  
  The smallest molecule is the diatomic hydrogen (H), with a bond length of 0.74 Å.
  
  Effective molecular radius is the size a molecule displays in solution. The table of permselectivity for different substances contains examples.