CHEMISTRY GLOSSARY

semiconductor    →   poluvodič

Semiconductor is a material in which the highest occupied energy band (valence band) is completely filled with electrons at T = 0 K, and the energy gap to the next highest band (conduction band) ranges from 0 to 4 or 5 eV. With increasing temperature electrons are excited into the conduction band, leading to an increase in the electrical conductivity.

silver    →   srebro

Silver has been known since ancient times. The origin of the name comes from the Latin word argentum meaning silver. It is silvery-ductile and malleable metal. Stable in water and oxygen. Reacts with sulfur compounds to form black sulfides. Silver is found in ores called argentite (AgS), light ruby silver (Ag₃AsS₃), dark ruby silver (Ag₃SbS₃) and brittle silver. Used in alloys for jewellery and in other compounds for photography. It is also a good conductor, but expensive.

spin    →   spin

Spin is the intrinsic angular momentum of an elementary particle, or system of particles such as nucleus, that is also responsible for the magnetic moment; or, a particle or nucleus possessing such a spin. The spins of nuclei have characteristic fixed values. Pairs of neutrons and protons align to cancel out their spins, so that nuclei with an odd number of neutrons and/or protons will have a net non-zero rotational component characterized by a non-zero quantum nuclear spin number.

Stern-Gerlach experiment: a beam of silver atoms is split into two beams when it traverses a nonuniform magnetic field. Atoms with spin quantum number m_s=+1/2 follow one trajectory, and those with m_s=+1/2 follow another.

tungsten    →   volfram

Tungsten was discovered by Fausto and Juan Jose de Elhuyar (Spain) in 1783. Named after the tungsten mineral wolframite. It is hard, steel-grey to white metal. Highest melting point of all metals. Resists oxygen, acids and alkalis. Tungsten occurs in the minerals scheelite (CaWO₄) and wolframite [(Fe,Mn)WO₄]. Made into filaments for vacuum tubes and electric lights. Also as contact points in cars. Tungsten carbide is extremely hard and is used for making cutting tools and abrasives.

Volta, Alessandro    →   Volta, Alessandro

The Italian physicist Alessandro Giuseppe Antonio Anastasio Volta (1745-1827) was the inventor of the voltaic pile, the first electric battery (1800). In 1775 he invented the electrophorus, a device that, once electrically charged by having been rubbed, could transfer charge to other objects. Between 1776 and 1778, Volta discovered and isolated methane gas (CH₄). The electrical unit known as the volt was named in his honor.

voltaic pile    →   Voltin stup

Voltaic pile was the first device that produced a continuous electric current. The first piles constructed by the Italian physicist Alessandro Volta (1745-1827) in 1800 comprised alternating silver and zinc discs separated by cardboard soaked in brine. The pile can be stacked as high as you like, and each layer will increase the voltage by a fixed amount.

xenon    →   ksenon

Xenon was discovered by Sir William Ramsay, Morris W. Travers (England) in 1898. The origin of the name comes from the Greek word xenos meaning stranger. It is heavy, colourless, odourless, noble gas. Reacts only with fluorine. Xenon is obtain from the small quantities in liquid air. Used for filling flash lamps and other powerful lamps. Electrical excitation of xenon produces a burst of brilliant white light. Also used in bubble chambers and modern nuclear power reactors.

Zeeman effect    →   Zeemanov efekt

Zeeman effect is the splitting of the lines in a spectrum when the source of the spectrum is exposed to a magnetic field. The effect was discovered in 1896 by the Dutch physicist Pieter Zeeman (1865-1943) as a broadening of the yellow D-lines of sodium in a flame held between strong magnetic poles.

The Zeeman effect has helped physicists determine the energy levels in atoms. In astronomy, the Zeeman effect is used in measuring the magnetic field of the Sun and of other stars.