Sir William Ramsay was a Scottish scientist. He was born in 1852 in Glasgow and died in 1916. He discovered the inert gases which include helium, argon and neon. Research William Ramsay
Argon is a colourless, odourless, gaseous element found in the air and volcanic gases, and is used especially as a filler for electric bulbs and electron tubes. It has the symbolAr.
Argon was found to exist in the atmosphere in small quantity (about one percent of the whole), its discovery being due to LordRayleigh and Professor Ramsay in 1894. Its discovery was led up to by the fact that the density of nitrogen as derived from the atmosphere differs from its density as derived from other sources, and this difference was found to be due to the presence of argon, which is about half as heavy again as nitrogen. The new substance was named argon by its discoverers on account of its chemical inertness (from Greek a, not, ergon work), that is, its refusal to form compounds by combining with other substances. Ramsay since showed that this 'argon' consists of a mixture of five hitherto unknown gaseous elements termed helium, neon, argon, krypton, and xenon - now called the noble gases. The amounts are extremely small; thus by volume 0.937 of argon per 100, 1 or 2 of neon per 1000,1 or 2 of helium per 1,000,000; similarly for krypton and xenon, 1 per 20 million. At the time of their discovery they were considered to be of no general importance. Research Argon
Valency is the maximum combining power of a chemical element. The valency is expressed in relation to the number of hydrogen atoms with which one atom of another element can combine. For example, chlorine, bromine, and iodine combine with or can replace one atom of hydrogen, these elements being called univalent or monads. When an element such as oxygen combines with two atoms of hydrogen it is termed bivalent or dyad, when with three atoms (egnitrogen), trivalent or triad, and with four (egcarbon), quadrivalent or tetrad.
Other elements show higher valencies, the terms used being quinquivalent or pentad, sexivalent or hexad, septivalent or heptad, and octavalent or octad. Where an element such as argon does not combine with another element it is said to be non-valent. The valency of the elements has been ascertained by experiment.
Valencies are indicated in what are known as graphic symbols by bonds, eghydrogen chloride (hydrochloric acid) is shown as H-Cl. There is, however, the difficulty that some elements do not exhibit a constant valency. Phosphorus, for instance, combines with chlorine in two proportions, one containing three atoms of chlorine, and the other five, To explain this it is suggested that there are differences in the condition of the atoms, especially in their states of motion. Research Valency
Vapour deposition is a method of manufacturing materials, particularly in the form of thin films, by the deposition of gas or vapour atoms or molecules on a substrate.
In chemical vapour deposition (CVD), the gas or vapour decomposes in a surface reaction to form a solid layer: decomposition is activated either by heat or by direct excitation using laser light. CVD is used to manufacture semiconductor devices, wear-resistant ceramic films, diamond films, and ceramic or glass fibres.
In physical vapour deposition (PVD) the vapour, produced by high-temperature evaporation of a solid or liquid in a vacuum, is condensed on to the substrate. PVD is used to manufacture semiconductor devices, and to evaporate thin layers of aluminium on to plastic food packaging films, or on to polycarbonate discs in the manufacture of compact discs. A vapour can also be produced at normal temperatures by the technique of sputtering. Sputtering is a physical process in which ions extracted from an inert gas (for example, argon) are accelerated and bombarded upon the solid target material that is to be deposited. The target atoms are ejected by this bombardment and deposit on a substrate. Sputtering is used mostly in the deposition of metals, which are difficult to deposit by other means. Research Vapour Deposition
A is an abbreviation for Acting
A is an abbreviation for effective aperture area of antenna
A is an abbreviation for Academician
A is an abbreviation for Academy
A is an abbreviation for Accepted
A is an abbreviation for Active
A is an abbreviation for Adjective
A is an abbreviation for Adult
A is an abbreviation for Aftermath
A is an abbreviation for Advanced
A is an abbreviation for Ampere
A is an abbreviation for Analog
A is an abbreviation for Ante
A is an abbreviation for Angstrom
A is an abbreviation for Area
A is an abbreviation for Argon
A is an abbreviation for Associate
A is an abbreviation for Atomic
A is an abbreviation for Acre
A is an abbreviation for America
A is an abbreviation for Amateur
A is an abbreviation for Answer
A was formerly an abbreviation for Argon
AR is an abbreviation for Argentina
AR is an abbreviation for Address Register
AR is an abbreviation for Arkansas
AR is an abbreviation for Autonomous Republic
AR is an abbreviation for Accounts Receivable
AR is an abbreviation for Acknowledgement of Receipt
AR is an abbreviation for AURail
AR is an abbreviation for All Risks
AR is an abbreviation for Amplifier Research
AR is an abbreviation for Angle Ranging
AR is an abbreviation for Annual Return
AR is an abbreviation for Army Regulation
Ar is an abbreviation for Argon Research AR
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Abbreviations
Research William Ramsay
