Molecule
A molecule is a group of two or more atoms which form one unit linked together by covalent bonds. Molecules can have as many as several thousand atoms, as in a polymer (see also DNA). A molecule typically does not have electrical charge (see also polyatomic ion).
Most molecules are composed of two or more elements, but they can also be composed of multiple atoms from the same element. Single element, bimolecular molecules which are more commonly known as homonuclear diatomic molecules <ref>http://xbeams.chem.yale.edu/~batista/vvv/node33.html</ref><ref>http://www.chem.purdue.edu/gchelp/gloss/homodiatomic.html</ref> include many elementary gases, such as oxygen (O2), hydrogen (H2) and fluorine (F2). Single element compounds also include man-made compounds such as buckminsterfullerenes, which are “balls” of 60 carbon atoms, as well as natural carbon compounds like graphite and diamonds, and most metals.
Molecules are typically specified by indicating what atoms they are made of and how many of each they possess. If there is more than one of an atom, its count is given by a subscript. Water has two hydrogen atoms and one oxygen atom, so it is H2O.
Often part of the molecule is listed separately in order to show some of its properties. There are more complex, but still text based, ways of “describing” the molecule's entire structure. We also use three dimensional “ball and stick” or “space filling” diagrams to show the complete physical arrangement of the atoms in the molecule.
See also
- Snippet from Wikipedia: Molecule
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and biochemistry, the distinction from ions is dropped and molecule is often used when referring to polyatomic ions.
A molecule may be homonuclear, that is, it consists of atoms of one chemical element, e.g. two atoms in the oxygen molecule (O2); or it may be heteronuclear, a chemical compound composed of more than one element, e.g. water (two hydrogen atoms and one oxygen atom; H2O). In the kinetic theory of gases, the term molecule is often used for any gaseous particle regardless of its composition. This relaxes the requirement that a molecule contains two or more atoms, since the noble gases are individual atoms. Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are typically not considered single molecules.
Concepts similar to molecules have been discussed since ancient times, but modern investigation into the nature of molecules and their bonds began in the 17th century. Refined over time by scientists such as Robert Boyle, Amedeo Avogadro, Jean Perrin, and Linus Pauling, the study of molecules is today known as molecular physics or molecular chemistry.