Chemistry & Environmental Dictionary

Electrical Conductivity - EPA

Electrical Conductivity

See Conduction

Electrochemical equivalents

An element's mass displaced by a unit quantity of electricity passage. The formula used on this site is: electrochemical equivalents=kA/n. 'k' is a constant that equals 0.0373100, 'A' is the gram-atomic weight and 'n' is the principle valence.


A measure of the ability of an atom in a molecule to draw bonding electrons to itself. This is partially determined by how many electron vacancies are available in an element's filling orbital. The most electronegative elements are the halogens, which have only one vacancy (i.e. have seven electrons in their filling orbital). Sulfur and oxygen are also highly electronegative.


A particle of matter that has a negative electric charge of 4.8 E -10 esu and a mass of 9.1E -28g or 1/1837 the mass of a proton. They can be found as a constituent part of an atom orbiting around the nucleus or in the free state. Electrons are arranged around the nucleus of an atom in from one to seven orbitals with the number of electrons in each orbital is strictly limited by the laws of physics. More information

Electron work function (photoelectric work function)

The smallest amount of photonic energy necessary to remove an electron from the boundary of an element.


One of the 116 presently known substances that cannot be decomposed by chemical reaction into a simpler substance. Elements comprise all matter at and above the atomic level. All elements heavier than lead (Pb) are radioactive and unstable. In addition, there are no stable elements with odd numbers of both protons and neutrons heavier than nitrogen (N). Elements with even numbers of protons and an even number of neutrons make up about 90% of the earth's crust.

Energy Levels (electron shells, shells)

The possible locations around an atom where electrons having specific energy values (quantum number) may be found. The term shell has been replaced with the term energy levels because the term shell insinuated that electrons circled the atom in fixed orbits like planets circle the sun. This model however is incorrect and outdated. Although the term shell is outdated, it is still often used grade school and high school science classes, as its concepts are less intimidating than are the use of terms like quantum number. More information

EPA (Environmental Protection Agency)

Created in 1970 as an agency of the United States federal government, charged with protecting the environment and enforcing environmental laws and regulations. The EPA did not play a significant role in waste management until RCRA was inacted in 1976 in response to the Love Canal incident.

Emergency Response Guidebook (ERG)

This guidebook, which is produced by the US Department of Transportation, assists responders in making initial decisions upon arriving at the scene of a dangerous goods incident. The 1996 edition of this guide was called the NAERG (North American Emergency Response Guidebook), however, the 2000 edition reverted back to the original name. (online version of ERG)


The sudden and violent release of mechanical, chemical or nuclear energy from a confined space which creates a heat wave that travels at subsonic speeds. Often used interchangeably with detonation.

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