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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Disproportionation Reactions
Redox reactions in which the oxidizing agent and the reducing agent are the same species.
Compressed Gas
A gas or mixture of gases having, in a container an absolute pressure exceeding 40 psi at 21.1°C (70°F)
Fatty Acids
An aliphatic acid, many can obtained from animal fats.
Ionization Constant
Equilibrium constant for the ionization of a weak electrolyte.
Stoichiometry
Description of the quantitative relationships among elements and compounds as they undergo chemical changes.
Dermal toxicity
Adverse health effects resulting from skin exposure ot a substance.
Pairing
A favourable interaction of two electrons with opposite m , values in the same orbital.
Enzyme
A protein that acts as a catalyst in biological systems.
What are Compound Microscopes?
Most of the microscopes used today are compound. A compound microscope features two or more lenses. A hollow cylinder called the tube connects the two lenses.
The top lens, the one people look through, is called the eyepiece. The bottom lens is known as the objective lens. Below the two lenses is the stage, with the illuminator below that.
Ether
Compound in which an oxygen atom is bonded to two alkyl or two aryl groups, or one alkyl and one aryl group.
