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).
Protactinium was discovered by Otto Hahn (Germany) and Lise Meitner (Austria) in 1917. The origin of the name comes from the Greek word protos meaning first. It is very rare, silvery-white, extremely radioactive metal. Resists alkalis; reacts with oxygen and acids. Attacked by steam. Highly radiotoxic. Protactinium is extremely toxic and must be handled with great care. Protactinium does not occur in nature. Found among fission products of uranium, thorium and plutonium.
Radium was discovered by Marie and Pierre Curie (France) in 1898. The origin of the name comes from the Latin word radius meaning ray. It is silvery-white radioactive metal. Reacts with oxygen and water. Highly radiotoxic. Carcinogen by inhalation, ingestion, or exposure. Radium is found in uranium ores at 1 part per 3 million parts uranium. Used in treating cancer because of the gamma rays it gives off.
Silicon was discovered by Jöns Jacob Berzelius (Sweden) in 1824. The origin of the name comes from the Latin word silicis meaning flint. Amorphous form of silicon is brown powder; crystalline form has grey metallic appearance. Solid form unreactive with oxygen, water and most acids. Dissolves in hot alkali. Silica dust is a moderately toxic acute irritant. Silicon makes up major portion of clay, granite, quartz and sand. Commercial production depends on a reaction between sand (SiO2) and carbon at a temperature of around 2200 °C. Used in glass as silicon dioxide (SiO2). Silicon carbide (SiC) is one of the hardest substances known and used in polishing. Also the crystalline form is used in semiconductors.
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.
Spontaneous process is a process that occurs without outside intervention. No external forces are required to keep the process going, although external forces may be required to get the process started. For example, the burning of wood is spontaneous once the fire is started. The combination of water and carbon dioxide to reform the wood and oxygen is NOT spontaneous! Spontaneity is independent of rate. To be spontaneous a process must increase the entropy of the universe.
Stoichiometry is the relative proportions elements from compounds or in which substances react. Every chemical reaction has its characteristic proportions. For example, when methane unites with oxygen in complete combustion, 1 mol of methane requires 2 mol of oxygen.
At the same time, 1 mol of carbon dioxide and 2 mol of water are formed as reaction products.
Alternatively, 16 g of methane and 64 g of oxygen produce 44 g of carbon dioxide and 36 g of water.
The stoichiometric relationship between the products and reactants can be used to in calculations.
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.
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.
Tellurium was discovered by Franz Joseph Muller von Reichstein (Romania) in 1782. The origin of the name comes from the Latin word tellus meaning earth. It is silvery-white, brittle semi-metal. Unreactive with water or HCl; dissolves in HNO3; burns in air or oxygen. Tellurium is obtained as a by-product of copper and lead refining. Used to improve the machining quality of copper and stainless steel products and to colour glass and ceramics. Also in thermoelectric devices. Some is used in the rubber industry and it is a basic ingredient in manufacturing blasting caps.
Generalic, Eni. "Oxygen meter for oxygen concentrator." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
Glossary
Periodic Table