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Refers to substances that crystallize in more than one crystalline arrangement.

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Chemical Hygiene Officer (CHO)

A person or employee who is qualified by training or experience to provide technical guidance in the development and implementations of the provisions of a Chemical Hygiene Plan (CHP)

Electronic Transition

The transfer of an electron from one energy level to another.

Substitution Reaction

A reaction in which an atom or a group of atoms is replaced by another atom or group of atoms.

Electrolytic Conduction

Conduction of electrical current by ions through a solution or pure liquid.

Covalent Bond

Chemical bond formed by the sharing of one or more electron pairs between two atoms.

Dissociation Constant

Equilibrium constant that applies to the dissociation of a comples ion into a simple ion and coordinating species (ligands).

Barometer

A device for measuring pressure.

Composition Stoichiometry

Descibes the quantitative (mass) relationships among elements in compounds.

Sublimation

The direct vaporization of a sold by heating without passing through the liquid state.

Ampere

Unit of electrical current, one ampere equals one coulomb per second.

 

Molecular Formula

Formula that indicates the actual number of atoms present in a molecule of a molecular substance.

Quantum Numbers

Numbers that describe the energies of electrons in atoms, derived from quantum mechanical treatment.

Equivalent Weight

An oxidizing or reducing agent, who's mass gains (oxidizing agents) or loses (reducing agents) 6.022 x 1023 electrons in a redox reaction.
The mass of an acid or base that furnishes or reacts with 6.022 x 1023 H3O+ or OH- ions.

Hydrogen

Discovered : by Henry Cavendish in 1766.
Isolated in London, UK.
Origin : The name is derived from the Greek ‘hydro genes’, meaning water forming.
Description :A colourless, odourless gas that burns and can form an explosive mixture with air. It is currently manufactured from methane gas, but is also produced by the electrolysis of water and aqueous salts. The gas is used to make such key materials as ammonia, cyclohexane and methanol, which are intermediates in the production of fertilisers, plastics and pharmaceuticals. Some see hydrogen gas as the clean fuel of the future - generated from water and returning to water when it is oxidised. Hydrogen-powered fuel cells are increasingly being seen as pollution-free sources of energy.

Acyl Group

Compound derived from a carbonic acid by replacing the --OH group with a halogen (X), usually --Cl, general formula is O R--C--X.

Electromotive Series

The relative order of tendencies for elements and their simple ions to act as oxidizing or reducing agents, also called the activity series.

Ionization Isomers

Isomers that result from the interchange of ions inside and outside the coordination sphere.

yttrium

A rare trivalent metallic element, found in gadolinite and other minerals. Symbol: Y, at. wt.: 88.905, at. no.: 39, sp. gr.: 4.47. Cf."rare-earth element."

Yttrium has a silver-metallic luster and is relatively stable in air unless finely divided. Turnings of the metal, however, ignite in air if their temperature exceeds 400oC. Yttrium oxide is one of the most important compounds of yttrium and accounts for the largest use. It is widely used in making YVO4 europium, and Y2O3 europium phosphors to give the red color in color television tubes.

Mother Nuclide

Nuclide that undergoes nuclear decay.

Conduction Band

A partially filled band or a band of vacant energy levels just higher in energy than a filled band, a band within which, or into which, electrons must be promoted to allow electrical conduction to occur in a solid.