MM. Molecules

MM. Molecules.

Molecules are compounds of two or more atoms. These are sometimes of the same element (O2) or different elements (H2O). There is some debate about what sorts of bonds between atoms qualify as molecules. These debates can be captured in links between bonds [See MB. Chemical Bonds] and molecules.

The term molecule is sometimes restricted to compounds without electrical charge. Ions are (atoms or) compounds with electrical charge, and will be treated here as a subset of the molecule class and indicated by numbers and underlined numbers as was the case with ions of elements above [See ME. Chemical Elements].

Molecules are usually also defined as the smallest unit of a substance that carries its physical and chemical characteristics. The guiding principle of this classification is that natural objects be defined in terms of their essence rather than function, and thus that element of the definition is eschewed here. Notably, this spares us from addressing the fact that most minerals and crystals (and many other substances) cannot be identified in terms of typical molecules but rather represent more complex combinations. Such complex combinations can be represented as necessary using compound notation.

Individual molecules can be represented by their chemical formula:

MMH2O is water molecule.

There is no widely accepted exhaustive classification of types of molecules at present. Chemists have developed classifications of some of the more common types of chemical compounds: See MD. Descriptive Chemical Compounds.

See also MI. Isomers.

Molecules can be distinguished by the type of structure. See MS. Molecular Structure

Molecules can be distinguished by the type of bonds. See MB. Chemical Bonds

Various other types of molecules might be distinguished by compound notation:

· Number of atoms MM(MC2#number)

· Number of different elements MM(ME#number)

· The columns and perhaps rows from which atoms are drawn (or the valency which reflects the likelihood of gaining or losing electrons) e.g. MM (MT1 + MT3)

· Stability (molecules are supposed to be stable, but we might include unstable molecules too, especially as there is some debate over the standard for stability) MM∩QC8 is not very stable.

· Type of bonds e.g. MM(MB1)

· Polarity (where electrical charge is not spread evenly through the molecule) MM (QN7(QR5)) is a possible notation.

Note The Art and Architecture Thesaurus has such chemical types as acid, base, inert, corrosive, chemical resistant, impure, pyroclastic, sorbent, and surface agent. These are all best captured through linked notation.

Some other useful examples of linked notation are provided here: Some Useful Compound Terms

Note on the word "Chemical": Every substance is a chemical. The word is sometimes used more narrowly to mean ‘compound’ or alternatively ‘substance generated by humans on purpose’. Users should be guided to more precise terms.