Astronomical unit (AU) is a unit of length employed in astronomy for describing planetary distance. It is the mean distance of the earth from the sun, equal to 1.49597870×1011 m.
Atmospheric pressure is the pressure exerted by weight of the air above it at any point on the earth’s surface. At sea level the atmosphere will support a column of mercury about 760 mm high. This decreases with increasing altitude. The standard value for the atmospheric pressure at sea level in SI units is 101 325 Pa.
Cosmic rays are high energy (1015 eV- 1017 eV) nuclear particles, electrons, and photons, originating mostly outside the solar system, which continually bombard the Earth’s atmosphere.
Argon was discovered by Lord Raleigh and Sir William Ramsay (Scotland) in 1894. The origin of the name comes from the Greek word argos meaning inactive. It is colourless and odourless noble gas. Chemically inert. It is the third most abundant element in the earth’s atmosphere and makes up about 1 %. Argon is continuously released into the air by decay of radioactive potassium-40. Pure form is obtained from fractional distillation of liquid air. Used in lighting products. It is often used in filling incandescent light bulbs. Some is mixed with krypton in fluorescent lamps. Crystals in the semiconductor industry are grown in argon atmospheres.
1. Atmosphere is the column of air which is extending several hundred kilometers above the surface the Earth's surface. The density of this air decreases as you proceed up from the surface. The air in the atmosphere consists of 78 % nitrogen, 21 % oxygen, and 0.9 % argon. The remaining 0.1 % of the atmosphere consists of ozone, water vapor, carbon dioxide, methane, helium, and neon. The atmosphere is divided into different regions. The lowest two layers are the troposphere (the layer closest to the earth) and the stratosphere respectively. These two layers contain more than 99 % of the atmospheric molecules.
2. Standard atmosphere (atm) is an obsolete pressure and stress unit which should be discontinued. It is unit of pressure equal to the air pressure measured at mean sea level.
1 atm = 101 325 Pa
Technical atmosphere (at) is an obsolete MKpS pressure and sttress derived unit.
1 at = 98 066.5 Pa
1 atm = 1.033 227 453 at
Cerium was discovered by Martin Heinrich Klaproth (Germany) and by Jöns Jacob Berzelius (Sweden) in 1803 and Wilhelm von Hisinger (Germany) in 1814. Named after the asteroid Ceres this discovered two years before the element. It is malleable, ductile, iron-grey metal. Tarnishes in air; reacts easily with water. Dissolves in acids; ignites when heated. Metal ignites and burns readily. Strong reductant. Cerium is most abundant rare earth metal. Found in many minerals like monazite sand [Ce(PO4)]. Its oxides are used in the optics and glass-making industries. Its salts are used in the photography and textile industry. Used in high-intensity carbon lamps and as alloying agents in special metals.
Cyanide process is a method for separating a metal from an ore. Crushed ore is treated with cyanide ion to produce a soluble metal cyanide complex. The complex is washed out of the ore and reduced to metallic form using an active metal (usually zinc).
Geochemistry is the scientific study of the chemical composition of the Earth. It includes the study of the abundance of the Earth’s elements and their isotopes and the distribution of the elements in environments of the Earth (lithosphere, atmosphere, biosphere, and hydrosphere).
Generalic, Eni. "Earth%E2%80%99s crust." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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