Oxygen was discovered by Joseph Priestley (England) in 1774. The origin of the name comes from the Greek words oxy genes meaning acid and forming (acid former). It is colourless, odourless gas; pale blue liquid. Extremely reactive. Forms oxides with nearly all other elements except noble gases. It is the most abundant element in the earth’s crust and makes up almost 21 % of the atmosphere. Oxygen is obtained primarily from liquid air by fractional distillation. Small amounts are made in the laboratory by electrolysis of water. Used in steel making, welding and supporting life. Naturally occurring ozone (O3) in the upper atmosphere shields the earth from ultraviolet radiation.
Phosphorescence is emission of light from a substance exposed to radiation and persisting as an afterglow after the exciting energy has been removed. Unlike fluorescence, in which the absorbed energy is spontaneously emitted about 10-8 second after excitation, phosphorescence requires additional excitation to produce radiation and may last from about mili second to days or years, depending on the circumstances.
Photochemical reactions are those reactions which are conducted under the influence of light that is under the influence of ultraviolet, visible and infrared part of the light spectrum. Some systems can be influenced only by radiation that is absorbed by that system. Photochemical reactions are for example photosynthesis, creation of photography, generation of phosgene, creation of hydrochloride etc.
Photomultiplier (photomultiplier tube or PMT) is a very versatile and sensitive detector of radiant energy in the ultraviolet, visible, and near infrared regions of the electromagnetic spectrum. A typical photomultiplier tube consists of a photoemissive cathode (photocathode) followed by focusing electrodes, an electron multiplier (dynode) and an electron collector (anode) in a vacuum tube.
Piezoelectric effect is voltage produced between surfaces of a solid dielectric (nonconducting substance) when a mechanical stress is applied to it. A small current may be produced as well. The effect, discovered by the French physicist Pierre Curie (1859-1906) in 1883, is exhibited by certain crystals, e.g., quartz and Rochelle salt, and ceramic materials. When a voltage is applied across certain surfaces of a solid that exhibits the piezoelectric effect, the solid undergoes a mechanical distortion. Piezoelectric materials are used in transducers, e.g., phonograph cartridges, microphones, and strain gauges, which produce an electrical output from a mechanical input, and in earphones and ultrasonic radiators, which produce a mechanical output from an electrical input.
Spectroscope (spectrometer) is an instrument for measuring the spectrum of light or radiation
Spontaneously combustible materials are materials that can ignite without an external source of heat. Heat sufficient to reach the ignition temperature may be generated by reaction with oxygen in the air, by the absorption of moisture, from heat generated during processing, or even from radioactive decay.
Termination is the final step in a free radical mechanism that results in the stopping of the free radical reaction.
Plutonium was discovered by Glenn T. Seaborg, Edwin M. McMillan, J. W. Kennedy and A. C. Wahl (USA) in 1940. Named after the planet Pluto. It is silvery-white, extremely radioactive artificially produced metal. Reacts with oxygen and acids; resists alkalis. Attacked by steam. Highly toxic. Plutonium is found rarely in some uranium ores. Made by bombarding uranium with neutrons. Used in bombs and reactors. Small quantities are used in thermo-electric generators.
Generalic, Eni. "Radij." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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