Chemistry & Environmental Dictionary


IATA (International Air Transport Association)

A Geneva Switzerland based association that regulates international air transportation and publishes annual regulations for air shipments of hazardous materials.


Immediately dangerous to life and health. In the event of the accidental exposure to a chemical, this is the concentration below which an individual could escape within 30 minutes without experiencing any escape-impairing or irreversible health effects.

Inert Gasses

See Noble Gasses.

Inner-Transition Metals

The thirty elements of the Lanthanides and Actinides series, which are sub-series of the Transition Metals.


a chemically inactive element, compound or material. Because of their extremely low chemical activity the noble gasses are considered to be inert substances. This term is also used for substances that are added to mixtures, primarily for their bulk and weight.


The area where two immiscible phases of a dispersion come into contact. It may involve the same or different states of matter. There are five possible types: liquid/liquid (oil/water), liquid/gas (water/air), liquid/solid (water/clay), solid/gas (smoke/air), solid/solid (rubber carbon black).


An atom that has gained or lost one or more electrons and thus has either a positive (cation) or negative (anion) charge.

Ionic radius

The radius exhibited by an ion in an ionic crystal where the ions are packed together to a point where their outermost electronic orbitals are in contact with each other.


International Union of Pure and Applied Chemists, the standards body that among other things, makes recommendations regarding the names of newly discovered elements and forms other chemistry related standards (such as the labeling of groups on the periodic table).

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