Chapter: Periodic Classification of Elements
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Allotropy is the property of an element to exist in more than one physical forms having similar chemical properties but different physical properties. Carbon exists both in crystalline and amorphous allotropic forms. Diamond, graphite and fullerene are the crystalline forms of carbon. Coal, coke, wood charcoal, animal charcoal, lampblack, gas carbon, petroleum, coke and sugar charcoal are the different amorphous allotropes of carbon.
Covalent compounds have low melting and boiling points. Covalent compounds are non conductors of electricity this is due to the absence of free ions. Sharing of electrons results in a covalent bond. A Lewis structure is a type of shorthand notation. The Lewis dot structures provide a picture of the bonding in molecules in terms of the shared pairs of electrons and the octet rule.
The vital force theory received a severe blow when wohler prepared urea in the laboratory from inorganic compound ammonium cyanate in the laboratory. The unique properties of carbon such as tetravalency, catenation and formation of multiple bonds are responsible for it to form millions of compounds.
Functional groups are specific atoms, ions, or groups of atoms that have consistent properties. In organic chemistry, apart from hydrocarbons, there are other molecules where carbon forms bonds with other elements, such as halogens, oxygen, nitrogen and sulphur.
Coal and petroleum are the fossils fuels. Carbon compounds undergo different types of chemical reactions. All carbon compounds react with oxygen to produce heat and light along with carbon dioxide and water. This reaction of carbon with oxygen is called combustion.
Soaps are sodium salts of long chain carboxylic acids. The soapiness in soap comes from the sodium salts of fatty acids like stearic acid, oleic acid and palmitic acid.
Sometimes, soaps don’t lather well with hard water. Hard water contains calcium and magnesium, which combine with soap molecules to form insoluble precipitates. Detergents consist of long chain molecules such as sodium n-dodecyl benzene sulphonate and sodium n- dodecyl sulphate. The charged ends of these compounds do not form insoluble precipitates with the calcium and magnesium ions in water. Detergents are used in shampoos and products for cleaning clothes.
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