CHEMISTRY GLOSSARY

metal hydride    →   metalni hidrid

Metal hydrides are compounds formed of atoms of a metal combined with atoms of hydrogen in which hydrogen has an oxidation number -1.

metallic bond    →   metalna veza

Metallic bond is a electrostatic attraction binding the positive ions of a solid metal together by means of a "sea" of delocalised valence electrons

metallic glass    →   metalno staklo

Certain alloys can solidify by extremely rapid cooling out of melt without formation of a crystal lattice, that is in the amorphous form - such, amorphous alloys are so called metallic glasses. The alloy of zirconium, beryllium, titanium, copper, and nickel is one of the first metallic glasses that can be made in bulk and formed into strong, hard, useful objects.

Unlike pure metals and most metal alloys, metallic glasses have no regular crystalline structure. This lack of long range order or microstructure is related to such desirable features as strength and low damping which is one reason why the premier use for zirconium-based metallic glass is in the manufacture of expensive golf club heads. Metallic glasses can be quite strong yet highly elastic, and they can also be quite tough (resistant to fracture). Even more interesting are the thermal properties; for instance, just like an oxide glass, there is a temperature (called the glass transition temperature) above which a metallic glass becomes quite soft and flows easily. This means that there are lots of opportunities for easily forming metallic glasses into complex shapes.

aerogel    →   aerogel

Aerogel is a low-density porous transparent material that consists of more than 90 % air. Usually based on metal oxides or silica, aerogels are used as drying agents and insulators.

allotrope    →   alotrop

Allotropes are the elements which exist in two or more different forms in the same physical state. Allotropes generally differ in physical properties and may also differ in chemical activity.

Diamond, graphite and fullerenes are three allotropes of the element carbon. Graphite is a soft, black, slippery substance; by contrast, diamond is one of the hardest substances known. The different properties of the allotropes arise from their chemical structures. Diamonds typically crystallize in the cubic crystal system and consist of tetrahedrally bonded carbon atoms. Graphite crystallizes in the hexagonal system. In the fullerenes, the carbon atoms taking the form of a hollow sphere, ellipsoid, or tube.

In some cases, the allotropes are stable over a temperature range, with a definite transition point at which one changes into the other. For instance, tin has two allotropes: white (metallic) tin stable above 13.2 °C and grey (nonmetallic) tin stable below 13.2 °C.

The term allotropes may also be used to refer to the molecular forms of an element. Ozone is a chemically active triatomic allotrope of the element oxygen.

allotropy    →   alotropija

Allotropy (Gr. allos, other, and tropos, manner) is the phenomenon of an element existing in two or more physical forms in the same physical state. The difference between the forms involves either crystaline structure (white, red and black phosphorus), the number of atoms in the molecule of a gas (diatomic oxygen and triatomic ozone), or the molecular structure of a liquid (liquid helium an helium II).

In some cases, the allotropes are stable over a temperature range, with a definite transition point at which one changes into the other. For instance, tin has two allotropes: white (metallic) tin stable above 13.2 °C and grey (nonmetallic) tin stable below 13.2 °C. This form allotropy is called enantiotropy. Form of allotropy, in which there is no transition temperature at which the two are in equilibrium, is called monotropy.

Allotropy does not apply to the substance existing in different physical states as, for example, when ice melts and changes from solid ice to liquid water.

Allotropy is generally restricted to describing polymorphic behaviour in elements, while polymorphism may refer to any material having multiple crystal structures.

barrier film    →   barijerni film

Barrier film is a thin, continuous, non-porous, electrically insulating film on metal surfaces (usually comprised of oxides).

beta radiation    →   beta zračenje

Streams of beta particles are known as beta ray or beta radiation. Beta rays may cause skin burns and are harmful within the body. A thin sheet of metal can afford protection to the skin.

blanching    →   blanširanje

1. Blanching is a heat treatment of foodstuffs to partially or completely inactivate the naturally occurring enzymes prior to freezing.

2. Blanching is a washing process for coins cleaning. The black surface layer of cupric oxide is removing by dipping the coins in hot dilute sulphuric acid (w(H₂SO₄) = 10 %).

antimony    →   antimon

Antimony has been known since ancient times. The origin of the name comes from the Latin word stibium meaning mineral stibnite. It is hard, brittle, silvery-white semimetal. Stable in dry air. Toxic by ingestion or inhalation. Antimony is found in stibnite (Sb₂S₃) and in valentinite (Sb₂O₃). It is alloyed with other metals to increase their hardness. Also in the manufacture of a few special types of semiconductor devices. Also in plastics and chemicals. A few kinds of over-the-counter cold and flu remedies use antimony compounds.