Organic Molecules

• Organic molecules are the building blocks of life. While it can be hard to define exactly what an organic molecule is, a commonly used criteria is that it will contain carbon, with the exception of a few very simple compounds which do contain carbon but which are not considered organic, for example carbon dioxide (CO2). Organic molecules range from small, simple carbon-based chemicals such as ethanol, hexane and acetic acid, all the way to large, complex compounds that make up living systems, including proteins, sugars and fatty acids.
  
  

Inorganic Molecules

• Inorganic molecules essentially include all the molecules that are not organic. There are many different types of inorganic compounds which can be placed into various subcategories. Some simple inorganic molecules are water (H2O), ammonia (NH3) and hydrogen peroxide (H2O2). Many others are made by the addition of oxygen to various elements. These include iron oxide (FeO) and chromic acid (CrO3). Still others are coordination complexes in which various metals such as cobalt have attached "ligands" including ammonia and chlorine.
  
  

Ionic Inorganic Compounds

• A further class of inorganic compounds that represents many species are the ionic molecules. These are chemicals where two or more atoms are held together by the electrostatic attraction between oppositely charged atoms, or ions. Examples include table salt (Na+ combined with Cl-), potassium perchlorate (KClO4) and sodium nitrate (NaNO3). These compounds tend to be readily soluble in water and split into their constituent ions when dissolved.
  
  

Polymers

• Polymers, also called macromolecules, are distinct because they are large compared to other molecules and are generally formed by joining together many smaller molecules like links in a chain. The long molecules tend to entangle each other and this gives polymers a degree of cohesiveness that compounds with smaller molecules lack. As well, polymer molecules are often springy and so these substances show properties such as flexibility and elongation. Some common examples of polymers are polyethylene, styrofoam and rubber.