CHEMISTRY GLOSSARY

valence shell    →   valentna ljuska

Valence shell is the shell corresponding to the highest value of principal quantum number in the atom. The valence electrons in this shell are on average farther from the nucleus than other electrons. They are often directly involved in chemical reaction.

accelerator    →   akcelerator

Accelerator is a device (machine) used for acceleration of charged particles (protons, deuterons, α-particles). Particles are accelerated under the influence of an electric field and with the help of a magnetic field are kept inside a certain space. When the particles reach enough acceleration (that is sufficient energy), they are directed on a target we wish to bomb. Best known types cyclotron, synchrotron, betatron.

Accelerator is a substance that increases the rate of chemical reaction, i.e. a catalyst.

accumulator    →   akumulator

Accumulator (secondary cell, storage battery) is a type of voltaic cell or battery that can be recharged by passing current through it from an external D.C. supply. The charging current reverses the chemical reactions in the cell. The common types are the lead-acid accumulator and the nickel-cadmium cell.

activated charcoal    →   aktivni ugljen

Activated charcoal or activated carbon is charcoal that has been activated for adsorption by steaming or by heating in a vacuum. Charcoal is obtained by burning wood, nutshells, coconut husks or other materials. Charcoal becomes activated by heating it with steam to approximately 1000 °C in the absence of oxygen.

The chemical nature of amorphous carbon, combined with a high surface area makes it an ideal medium for the adsorption of organic chemicals. A single gram of such material can have 400 m² to 1 200 m² square meters of surface area. Activated charcoal is widely used to decolorize liquids, recover solvents, and remove toxins from water and air.

activation energy    →   energija aktivacije

Activation energy (E_a) is the energy that must be added to a system in order for a process to occur, even though the process may already be thermodynamically possible. In chemical kinetics, the activation energy is the height of the potential barrier separating the products and reactants. It determines the temperature dependence on the reaction rate.

additive    →   aditivi

Additive is a substance added to a material to improve its properties in some way. Additives are often present in small amounts and are used for a variety of purposes, as in preventing corrosion, stabilizing polymers, and preserving and improving food.

ageing    →   starenje

Ageing is the physical and/or chemical change of a material with respect to time, under defined environmental conditions, leading to improvement or deterioration of properties.

allomerism    →   alomerija

Allomerism is the appearance of substances with different chemical composition but the same crystalline form.

analysis    →   analiza

Analysis. Chemical analysis is determination of the composition of a sample.

antacid    →   antacid

Antacid is any mildly alkaline substance, such as sodium bicarbonate, taken internally or in water solution to neutralize excess stomach acidity.