CHEMISTRY GLOSSARY

samarium    →   samarij

Samarium was discovered by Paul Emile Lecoq de Boisbaudran (France) in 1879. Named after the mineral samarskite. It is silvery rare earth metal. Stable in dry air. Oxide coating forms on surfaces exposed to moist air. Metal ignites and burns readily. Reacts with water. Samarium is found with other rare earths in monazite sand. It is used in the electronics and ceramics industries. It is easily magnetized and very difficult to demagnetise. This suggests important future applications in solid-state and superconductor technologies.

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.

sodium    →   natrij

Sodium was discovered by Sir Humphry Davy (England) in 1807. The origin of the name comes from the Latin word natrium meaning sodium carbonate. It is soft silvery-white metal. Fresh surfaces oxidize rapidly. Reacts vigorously, even violently with water. Reacts with water to give off flammable gas. Burns in air with a brilliant white flame. Sodium is obtained by electrolysis of melted sodium chloride (salt), borax and cryolite. Metallic sodium is vital in the manufacture of organic compounds. Sodium chloride (NaCl) is table salt. Liquid sodium is used to cool nuclear reactors.

standard electrode potential    →   standardni elektrodni potencijal

Standard electrode potential (E°) (standard reduction potentials) are defined by measuring the potential relative to a standard hydrogen electrode using 1 mol solution at 25 °C. The convention is to designate the cell so that the oxidised form is written first. For example,

The e.m.f. of this cell is -0.76 V and the standard electrode potential of the Zn²+|Zn half cell is -0.76 V.

strontium    →   stroncij

Strontium was discovered by Sir Humphry Davy (England) in 1808. Named after the village of Strontian in Scotland. It is soft, malleable, silvery-yellow metal. Combustible in air, will react with water. Exposed surfaces form protective oxide film. Metal ignites and burns readily. Strontium is found in minerals celestite and strontianite. Used in flares and fireworks for crimson colour. Strontium-90 is a long lived highly radioactive fallout product of atomic-bomb explosions.

superoxide    →   superoksid

Superoxides are binary compounds containing oxygen in the -½ oxidation state. Sodium superoxide (NaO₂) can be prepared with high oxygen pressures, whereas the superoxides of rubidium, potassium, and cesium can be prepared directly by combustion in air. These compounds are yellow to orange paramagnetic solids. Superoxide ion, O₂^-, has an unpaired electron, is not particularly stable, and spontaneously decomposes into peroxide over time.

They are strong oxidising agents that vigorously hydrolyze (react with water) to produce superoxide and oxygen gas.

tantalum    →   tantal

Tantalum was discovered by Anders Ekeberg (Sweden) in 1802. The origin of the name comes from the Greek word Tantalos meaning father of Niobe in Greek mythology, (tantalum is closely related to niobium in the periodic table). It is rare, grey, heavy, hard but ductile, metal with a high melting point. Exposed surfaces form corrosion resistant oxide film. Attacked by HF and fused alkalis. Metal ignites in air. Tantalum always found with niobium. Chiefly occurs in the mineral tantalite. Often used as an economical substitute for platinum. Tantalum pentoxide is used in capacitors and in camera lenses to increase refracting power. It and its alloys are corrosion and wear resistant so it is used to make surgical and dental tools.

technetium    →   tehnecij

Technetium was discovered by Carlo Perrier and Emilio Segre (Italy) in 1937. The origin of the name comes from the Greek word technikos meaning artificial. It is silvery-grey metal. Resists oxidation but tarnishes in moist air and burns in high oxygen environment. First synthetically produced element. Radioactive. Technetium is made first by bombarding molybdenum with deuterons (heavy hydrogen) in a cyclotron. Added to iron in quantities as low as 55 part-per-million transforms the iron into a corrosion-resistant alloy.

terbium    →   terbij

Terbium was discovered by Carl Gustaf Mosander (Sweden) in 1843. Named after Ytterby, a village in Sweden. It is soft, ductile, silvery-grey, rare earth metal. Oxidizes slowly in air. Reacts with cold water. Terbium is found with other rare earths in monazite sand. Other sources are xenotime and euxenite, both of which are oxide mixtures that can contain up to 1 % terbium. It is used in modest amounts in special lasers and solid-state devices.

thallium    →   talij

Thallium was discovered by Sir William Crookes (England) in 1861. The origin of the name comes from the Greek word thallos meaning green twig or green shoot. It is soft grey metal that looks like lead. Tarnishes in moist air. Reacts in heated moist air and in acids. Compounds highly toxic by inhalation or ingestion. Cumulative effects. Thallium is found in iron pyrites. Also in crookesite, hutchinsonite and lorandite. Most is recovered from the by-products of lead and zinc refining. Its compounds are used in rat and ant poisons. Also for detecting infrared radiation.