CHEMISTRY GLOSSARY

praseodymium    →   praseodimij

Praseodymium was discovered by Carl F. Auer von Welsbach (Austria) in 1885. The origin of the name comes from the Greek words prasios didymos meaning green twin. It is silvery white, moderately soft, malleable, ductile metal. Reacts slowly with oxygen. Reacts rapidly with water. Metal ignites and burns readily. Praseodymium is obtained from same salts as neodymium. Used with neodymium to make lenses for glass maker’s goggles since it filters out the yellow light present in glass blowing. Alloyed with magnesium creates a high-strength metal used in aircraft engines. Misch metal, used in the manufacture of pyrophoric alloys for cigarette lighters, contains about 5 % praseodymium metal. (Typically composition of misch metal are Ce:Nd:Pr:La:Other rare earth=50:18:6:22:4).

promethium    →   prometij

Promethium was discovered by J. A. Marinsky, Lawrence Glendenin and Charles D. Coryell (USA) in 1945. Named after Prometheus in Greek mythology, who stole fire from the gods. It is rare earth metal of synthetic origin on the earth, naturally made in stars. Poison. Radiotoxic. Radioactive. Promethium does not occur naturally. Found among fission products of uranium, thorium and plutonium. It has been used as a source of radioactivity for thickness-measuring gages.

proton    →   proton

Proton is a stable elementary particle of unit positive charge and spin 1/2. Protons and neutrons, which are collectively called nucleons, are the constituents of the nucleus.

In 1886, German physicist Eugene Goldstein (1850-1930) discovered positive particles by using a modified Crookes tube with holes in the cathode in an evacuated tube. When cathode rays were given off in one direction toward the anode, other rays found their way through the holes in the cathode and sped off in the opposite direction. Since these other rays traveled in the direction opposite to the negatively charged cathode rays, it seemed that they must be composed of positively charged particles. Rutherford suggested that this fundamental positive particle be called the proton.

resistivity    →   električna otpornost

Electrical resistivity, or specific resistance (ρ) is the electric field strength divided by the current density when there is no electromotive force in the conductor. Resistivity is an intrinsic property of a material. Materials with low resistivity are good conductors of electricity and materials with high resistivity are good insulators.

For a conductor of uniform cross section with area A and length L, and whose resistance is R, the resistivity is given by

The SI unit is Ω m.

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.

titanium    →   titanij

Titanium was discovered by William Gregor (England) in 1791. Named after the Titans, the sons of the Earth goddess in Greek mythology. It is shiny, dark-grey metal. Powdered form burns in air. Exposed surfaces form oxide coating. It can be highly polished and is relatively immune to tarnishing. Unreactive with alkali and most acids. Titanium usually occurs in the minerals ilmenite (FeTiO₃), rutile (TiO₂) and iron ores. Pure metal produced by heating TiO₂ with C and Cl₂ to produce TiCl₄ then heated with Mg gas in Ar atmosphere. Since it is strong and resists acids it is used in many alloys. Titanium dioxide (TiO₂), a white pigment that covers surfaces very well, is used in paint, rubber, paper and many others.

vanadium    →   vanadij

Vanadium was discovered by A. M. del Rio (Spain) in 1801 and rediscovered by Nils Sefstrom (Sweden) in 1830. Named after Vanadis, the goddess of beauty in Scandinavian mythology. It is soft, ductile, silvery-white metal. Resistant to corrosion by moisture, air and most acids and alkalis at room temperature. Exposed surfaces form oxide coating. Reacts with concentrated acids. Vanadium is found in the minerals patronite (VS₄), vanadinite [Pb₅(VO₄)₃Cl] and carnotite [K₂(UO₂)₂(VO₄)₂·3H₂O]. Pure metal produced by heating with C and Cl to produce VCl₃ which is heated with Mg in Ar atmosphere. It is mixed with other metals to make very strong and durable alloys. Vanadium pentoxide (V₂O₅) is used as a catalyst, dye and fixer-fixer.

zirconium    →   cirkonij

Zirconium was discovered by Martin Heinrich Klaproth (Germany) in 1789. The origin of the name comes from the Arabic word zargun meaning gold colour. It is grey-white, lustrous, corrosion-resistant metal. Exposed surfaces form oxide protective film. Zirconium is found in many minerals such as zircon and baddeleyite. Used in alloys such as zircaloy this is used in nuclear applications since it does not readily absorb neutrons. Also baddeleyite is used in lab crucibles. Used in high-performance pumps and valves. Clear zircon (ZrSiO₄) is a popular gemstone.