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Discovered : by Sir William Ramsay in London, and independently by P.T. Cleve and N.A. Langlet in Uppsala, Sweden in 1895.
Origin : The name is derived from the Greek ‘helios’,sun.
Description :A colourless, odourless gas that is totally unreactive. It is extracted from natural gas wells, some of which contain gas that is 7% helium. It is used in deep sea diving for balloons and, as liquid helium, for low temperature research. The Earth’s atmosphere contains 5 parts per million by volume, totalling 400 million tons, but it is not worth extracting it from this source at present.
Atomic No:2 MAss No:4

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Vapor

A gas formed by boiling or evaporating a liquid.

ytterbium

A rare metallic element found in gadolinite and forming compounds resembling those of yttrium. Symbol: Yb, at. wt.: 173.04, at. no.: 70, sp. gr.: 6.96. Cf."rare-earth element."

 

Nonelectrolyte

A substance whose aqueous solutions do not conduct electricity.

Hydrocarbons

Compounds that contain only carbon and hydrogen.

Differential Thermal Analysis (DTA)

A technique for observing the temperature, direction, and magnitude of thermally induced transitions in a material by heating/cooling a sample and comparing its temperature with that of an inert reference material under similar conditions.

Nonpolar Bond

Covalent bond in which electron density is symmetrically distributed.

Hard Water

Water containing Fe3+, Ca2+, and Mg2+ ions, which forms precipates with soap.

Colligative Properties

Physical properties of solutions that depend upon the number but not the kind of solute particles present.

Nuclear Reactor

A system in which controlled nuclear fisson reactions generate heat energy on a large scale, which is subsequently converted into electrical energy.

Dilution

Process of reducing the concentration of a solute in solution, usually simply by mixing with more solvent.

Covalent Compounds

Compounds containing predominantly covalent bonds.

Polarimeter

A device used to measure optical activity.

Electrical Conductivity

Ability to conduct electricity.

Evaporation Rate

The rate at which a particular substance will vapourize (evaporate) when compared to the rate of a known substance such as ethyl ether. This term is especially useful for health and fire-hazard considerations.

Phosphoric Acid

H3P04, Colorless liquid or rhombic crystals, decomposes before it will boil. Used mostly in the metal etchant. Used in cleaning operations to remove encrusted surface matter and mineral scale found on metal equipment such as boilers and steam producing equipment. Also used to brighten metals and remove rust.

Combustible

Classification of liquid substances that will burn on the basis of flash points. A combustible liquid means any liquid having a flash point at or above 37.8°C (100°F) but below 93.3°C (200°F), except any mixture having components with flash points of 93.3°C (200°F) or higher, the total of which makes up 99 percent or more of the total volume of the mixture.

Oxidation

An algebraic increase in the oxidation number, may correspond to a loss of electrons.

Electron

A subatomic particle having a mass of 0.00054858 amu and a charge of 1-.

Cathodic Protection

Protection of a metal (making ir a cathode) against corrosion by attaching it to a sacrifical anode of a more easily oxidized metal.

Nuclear Binding Energy

Energy equivalent of the mass deficiency, energy released in the formation of an atom from the subatomic particles.