DEFINE CHACOGENS AND ITS PROPERTIES IN DETAIL ( 5 MARKS ) PLEASE ANSWER ACCORDING TO MARKS.

Asked by IOUHIU OYYFGY | 19th Nov, 2010, 06:28: PM

Expert Answer:

Oxygen, sulphur, selenium, tellurium and polonium constitute the group 16 of the periodic table of elements.
 
The first four elements are collectively called CHALCOGENS.
 
 
The name derives from the Greek word for bronze and points to the association of sulphur and its congeners with copper.
 
All these are non-metallic in character. The metallic character increases down the group. The last element of the family, polonium has metallic character and is a radioactive element with a very short life period.
 
Properties:

Members of this group show similar patterns in their electron configuration, especially the outermost shells, resulting in similar trends in chemical behavior.

Oxygen and sulphur are nonmetals, and selenium, tellurium, and polonium are metalloid semiconductors that means, their electrical properties are between those of a metal and an insulator. Nevertheless, tellurium, as well as selenium, is often referred to as a metal when in elemental form.

Metal chalcogenides are common as minerals. For example, pyrite FeS2 is an iron ore. The rare mineral calaverite is the ditelluride AuTe2.

The formal oxidation number of the most common chalcogen compounds is −2. Other values, such as −1 in pyrite, can be attained. The highest formal oxidation number +6 is found in sulfates, selenates and tellurates, such as in sulfuric acid or sodium selenate Na2SeO4.

Answered by  | 20th Nov, 2010, 10:42: AM

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