Molecule



  In biomolecules. Molecules are distinguished from polyatomic ions in the strict sense.

This definition has evolved as knowledge of the structure of molecules has increased. Earlier definitions were less precise defining molecules as the smallest ions, but are not made of molecules.

In the noble gases would also be considered molecules despite the fact that they are composed of a single non-bonded atom.

History

Main article: History of the molecule

The term "molecule", from the French molécule meaning "extremely minute particle," was coined by French philosopher Rene Descartes in the 1620s. Although the existence of molecules was accepted by many chemists since the early 19th century as a result of Gibbs, who saw molecules merely as convenient mathematical constructs. The work of Perrin on Brownian motion (1911) is considered to be the final proof of the existence of molecules.

In a molecule, at least two atoms are joined by shared pairs of ionic bonds are generally not considered single molecules.

No typical molecule can be defined for ionic (sodium chloride).

The science of molecules is called molecular chemistry or Bose-Einstein condensates.

Molecular size

Most molecules are far too small to be seen with the naked eye, but there are exceptions. supermolecules.

Radius

Effective molecular radius is the size a molecule displays in solution. [5]. The table of permselectivity for different substances contains examples.

Molecular formula

The acetylene has molecular formula C2H2, but the simplest integer ratio of elements is CH. The molecular formula reflects the exact number of atoms that compose a molecule.

The formula unit is used in stoichiometric calculations.

Molecular geometry

Main article: Molecular geometry

Molecules have fixed 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 biochemical activities.

Molecular Theory

There are four statements of facts concerning molecules. These facts are:

1. All matter is composed of tiny particles called molecules.

2. There are spaces between molecules.

3. Molecules are constantly moving.

4. Molecules attract one another.

These statements together form the Molecular Theory, one of the fundamental theories in physics and chemistry.

Molecular spectroscopy

Main article: Spectroscopy

Molecular spectroscopy deals with the response (Scattering theory provides the theoretical background for spectroscopy.

The probing signal used in spectroscopy can be an emission spectroscopy), fragmentation, or chemical changes.

Spectroscopy is recognized as a powerful tool in investigating the microscopic properties of molecules, in particular their chemical computations.

Theoretical aspects

The study of molecules by computational chemistry.

When trying to define rigorously whether an arrangement of atoms is "sufficiently stable" to be considered a molecule, IUPAC suggests that it "must correspond to a depression on the helium dimer, He2, which has one vibrational bound state but is so loosely bound that it is only likely to be observed at very low temperatures.

Etymology

According to Merriam-Webster and the Online Etymology Dictionary, the word "molecule" derives from the Latin "moles" or small unit of mass.

  • Molecule (1794) - "extremely minute particle," from Fr. molécule (1678), from Mod.L. molecula, dim. of L. moles "mass, barrier". A vague meaning at first; the vogue for the word (used until late 18th century only in Latin form) can be traced to the philosophy of Descartes.

See also

References

  1. ^ a b International Union of Pure and Applied Chemistry (1994). "molecule". Compendium of Chemical Terminology Internet edition.
  2. ^ Pauling, Linus (1970). General Chemistry. New York: Dover Publications, Inc.. ISBN 0-486-65622-5. 
    Ebbin, Darrell, D. (1990). General Chemistry, 3th Ed.. Boston: Houghton Mifflin Co.. ISBN 0-395-43302-9. 
    Brown, T.L. (2003). Chemistry – the Central Science, 9th Ed.. New Jersey: Prentice Hall. ISBN 0-13-066997-0. 
    Chang, Raymond (1998). Chemistry, 6th Ed.. New York: McGraw Hill. ISBN 0-07-115221-0. 
    Zumdahl, Steven S. (1997). Chemistry, 4th ed.. Boston: Houghton Mifflin. ISBN 0-669-41794-7. 
  3. ^ Molecule Definition (Frostburg State University)
  4. ^ E.g. see [1]
  5. ^ [www.wipo.int/pctdb/en/wo.jsp?IA=WO1999030745&DISPLAY=DESC -(WO/1999/030745) DOTA-BIOTIN DERIVATIVES


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