Inorganic compounds are those that lack long carbon chains at their core. While some inorganic compounds contain carbon, they do not contain carbon that is bonded to hydrogen. Inorganic compounds include substances such as salt, carbon dioxide and water.
Organic compounds are typically associated with living organisms, while inorganic compounds are not usually important constituents of living bodies. Nevertheless, inorganic compounds are important chemicals for many organisms. For example, all living organisms require copious amounts of water and salt in small quantities. Carbon dioxide is a waste product of animals, but green plants require carbon dioxide to complete photosynthesis.
Part of the reason that organic molecules are involved in living systems is that they are often complex. Because inorganic molecules do not frequently become large or complex, there are not as many possibilities for using them as the building blocks of complicated systems. Organic molecules usually take the form of a large chain of molecules, with a core composed purely of carbon. Inorganic molecules do not have such long carbon chains.
The presence of carbon does not necessarily indicate that a molecule is organic. For example, carbides, carbonates, cyanides and a few other carbon-containing chemicals lack the long carbon chains and carbon-hydrogen bonds that characterize organic molecules.