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Main article: inorganic chemistry

Traditionally, inorganic compounds are considered to be of mineral, not biological, origin. Complementarily, most organic compounds are traditionally viewed as being of biological origin. Over the past century, the precise classification of inorganic vs organic compounds has become less important to scientists, primarily because the majority of known compounds are synthetic and not of natural origin. Furthermore most compounds considered the purview of modern inorganic chemistry contain organic ligands. The fields of organometallic chemistry and bioinorganic chemistry explicitly focus on the areas between the fields of organic, biological, and inorganic chemistry.

Inorganic compounds can be formally defined with reference to what they are not—organic compounds. Organic compounds are those which contain carbon, although some carbon-containing compounds are traditionally considered inorganic. When considering inorganic chemistry and life, it is useful to recall that many species in nature are not compounds per se but are ions. Sodium, chloride, and phosphate ions are essential for life, as are some inorganic molecules such as carbonic acid, nitrogen, carbon dioxide, water and oxygen. Aside from these simple ions and molecules, virtually all species covered by bioinorganic chemistry contain carbon and can be considered organic or organometallic.

Many compounds that contain carbon are considered inorganic; for example, carbon monoxide, carbon dioxide, carbonates, cyanides, cyanates, carbides, and thyocyanates. In general, however, workers in these areas are not concerned about strict definitions.

A large class of compounds discussed in inorganic chemistry textbooks are coordination compounds. Examples range from species that are strictly inorganic, such as [Co(NH₃)₆]Cl₃, to organometallic compounds such as Fe(C₅H₅)₂ and extending to bioinorganic compounds, such as the hydrogenase enzymes.

Minerals are mainly oxides and sulfides, which are strictly inorganic. In fact, most of the earth and the universe is inorganic (free of C-H containins species). Although the components of the earth's crust are well elucidated, the processes of mineralization and the composition of the deep mantle remain active areas of investigation, which are mainly covered in geology-oriented venues.

Major classes of inorganic compound are studied and developed by chemists trained in materials science. Species of interest tend to be polymeric (non-molecular) and refractory, and often such materials are of commercial interest. In general these inorganic compounds are classified based on their bulk properties, not their composition or structure:

• Alloys, such brass, bronze, and stainless steel
• Semiconductors such as silicon and gallium arsenide
• superconductors such as yttrium barium copper oxide

• List of inorganic compounds
• Inorganic compounds by element
• organic compound