CHEMISTRY GLOSSARY

actinium    →   aktinij

Actinium was discovered by André Debierne (France) in 1899. The origin of the name comes from the Greek word aktinos meaning ray. It is heavy, silvery-white, very radioactive metal. Reacts with water. Glows in the dark. Actinium is extremely rare, found in all uranium ores. Usually obtained by treating radium with neutrons in a reactor.

adhesion    →   adhezija

Adhesion is attraction between different substances on either side of a phase boundary. Adhesive is a substance used for joining surfaces together.

adrenaline    →   adrenalin

Adrenaline was the first naturally produced hormone to be isolated in its pure state. It is known as epinephrine, but its chemical name is 1-[3,4-dihydroxyphenol]-2-methylaminoethanol. Adrenaline is a hormone, produced by the medulla of the adrenal glands, that increases heart activity, improves the power and prolongs the action of muscles, and increases the rate and depth of breathing to prepare the body for "fright, flight, or fight". At the same time it inhibits digestion and excretion.

adsorbate    →   adsorbat

Adsorbate is a substance that is adsorbed on a surface.

adsorbent    →   adsorbent

Adsorbent is a substance on the surface of which a substance is adsorbed.

adsorption    →   adsorpcija

Adsorption is a process in which molecules of gas, of dissolved substances in liquids, or of liquids adheres in an extremely thin layer to surfaces of solid bodies with which they are in contact.

acid    →   kiselina

Acid is a type of compound that contains hydrogen and dissociates in water to produce positive hydrogen ions. The reaction for an acid HA is commonly written:

In fact, the hydrogen ion (the proton) is solvated, and the complete reaction is:

This definition of acids comes from the Arrhenius theory. Such acids tend to be corrosive substances with a sharp taste, which turn litmus red and produce colour changes with other indicators. They are referred to as protonic acids and are classified into strong acids, which are almost completely dissociated in water, (e.g. sulphuric acid and hydrochloric acid), and weak acids, which are only partially dissociated (e.g. acetic acid and hydrogen sulphide). The strength of an acid depends on the extent to which it dissociates, and is measured by its dissociation constant.

In the Lowry-Brønsted theory of acids and bases (1923), the definition was extended to one in which an acid is a proton donor (a Brønsted acid), and a base is a proton acceptor (a Brønsted base). An important feature of the Lowry-Brønsted concept is that when an acid gives up a proton, a conjugate base is formed that is capable of accepting a proton.

Similarly, every base produces its conjugate acid as a result of accepting a proton.

For example, acetate ion is the conjugate base of acetic acid, and ammonium ion is the conjugate acid of ammonia.

As the acid of a conjugate acid/base pair becomes weaker, its conjugate base becomes stronger and vice versa.

A further extension of the idea of acids and bases was made in the Lewis theory. In this, a G. N. Lewis acid is a compound or atom that can accept a pair of electrons and a Lewis base is one that can donate an electron pair. This definition encompasses "traditional" acid-base reactions, but it also includes reactions that do not involve ions, e.g.

in which NH₃ is the base (donor) and BCl₃ the acid (acceptor).

alkalinity    →   alkalitet

Alkalinity is a measure of a material’s ability to neutralize acids. It is usually determined using titration.

allomerism    →   alomerija

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

amino acids    →   aminokiseline

Amino acids are compounds containing both a carboxylic acid group (-COOH) and an amino group (-NH₂ ). The most important are the α-amino acids, in which the -NH₂ group in attached to the C atom adjacent to the -COOH group. In the β-amino acids, there is an intervening carbon atom.