Inorganic compounds comprise most of the Earth's crust, although the composition of the deep mantle remain active areas of investigation.
Inorganic compounds can be defined as any compound that is not organic compound. Some simple compounds that contain carbon are often considered inorganic. Examples include carbon monoxide, carbon dioxide, carbonates, cyanides, cyanates, carbides, and thiocyanates. Many of these are normal parts of mostly organic systems, including organisms, which means that describing a chemical as inorganic does not obligately mean that it does not occur within living things.
Friedrich Wöhler's conversion of ammonium cyanate into urea in 1828 is considered the starting point of modern organic chemistry. The Wöhler synthesis is of great historical significance because for the first time an organic compound (urea) was produced from inorganic precursors (the salt ammonium cyanate). This finding contradicted the then-mainstream theory vitalism, which stated that organic matter possessed a special force or vital force inherent to all things living. Prior to Wöhler's experiment, a sharp boundary was thought to separate organic and inorganic compounds.
- The Inorganic Crystal Structure Database (ICSD) in its definition of "inorganic" carbon compounds, states that such compounds may contain either C-H or C-C bonds, but not both.
- The book series Inorganic Syntheses does not define inorganic compounds. The majority of its content deals with metal complexes of organic ligands.
- IUPAC does not offer a definition of "inorganic" or "inorganic compound" but does define inorganic polymer as "...skeletal structure that does not include carbon atoms."
- Major textbooks on inorganic chemistry decline to define inorganic compounds: Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Francisco, 2001. ISBN 0-12-352651-5; Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9., Cotton, F. Albert; Wilkinson, Geoffrey (1988), Advanced Inorganic Chemistry (5th ed.), New York: Wiley-Interscience, ISBN 0-471-84997-9
- J. J. Berzelius "Lehrbuch der Chemie," 1st ed., Arnoldischen Buchhandlung, Dresden and Leipzig, 1827. ISBN 1-148-99953-1. Brief English commentary in English can be found in Bent Soren Jorgensen "More on Berzelius and the vital force" J. Chem. Educ., 1965, vol. 42, p 394. doi:10.1021/ed042p394
- Dan Berger, Bluffton College, analysis of varying inappropriate definitions of the inorganic-organic distinction: Otherwise consistent linked material differing from current article in downplaying the carbon present vs carbon absent distinctive:
- Newman, D. K.; Banfield, J. F. (2002). "Geomicrobiology: How Molecular-Scale Interactions Underpin Biogeochemical Systems". Science. 296 (5570): 1071–1077. doi:10.1126/science.1010716. PMID 12004119. Archived from the original on 2013-10-17.
- May, Paul. "Urea". Molecules in Motion. Imperial College London. Archived from the original on 2015-03-17.
- "Inorganic Crystal Structure Database" (PDF). Archived from the original (PDF) on 2017-08-30. Retrieved 2017-01-13.