What Is The Occurrence Of Sulphur And Its Allotropes?


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Shumaela Rana Profile
Shumaela Rana answered
The elemental sulphur has been known since prehistoric times and naturally exists in the earth crust (about 0.1%). It occurs in nature both in free and combined state. The elemental sulphur exists deep into the earth. In Free State sulphur is found in Mexico and the United States. In Pakistan, some deposits of native sulphur occur in Koh-I-Sultan and Kallat area. In the combined state, sulphur is found mostly in the form of sulphides and sulphate. Just like carbon, phosphorus and oxygen free sulphur can exist in several allotropes.

Free sulphur exists as rhombic sulphur in nature because it is the only stable allotrope at room temperature. Its crystals are bright yellow in color and octahedral in shape. They are made up of molecules. These molecules consist of eight sulphur atoms bound to each other through single covalent bond.

Monoclinic is another crystalline allotrope of sulphur. Its molecule also consists of eight atoms. The difference between rhombic and monoclinic sulphurs is in the arrangements of atoms. At room temperature the monoclinic sulphur is slowly converted into rhombic sulphur.

Plastic sulphur can not be considered to be true allotrope of sulphur because it is un stable and changes into rhombic sulphur on slight warming or on standing.
Saki Profile
Saki answered
Sulphur is found widely distributed in earth's crust. It is found in vast underground beds of 99.8% pure uncombined sulphur and in many sulphide minerals such as galena,pyrite ,sphalesite and various calcium, magnesium and other sulphates.Sulphur is also present in organic compounds.It is found in animals and vegetables such as onion, garlic, mustard, eggs, proteins etc. Sulphur also occurs along with hydrocarbons such as coal and petroleum.

There are three allotropic forms of sulphur which are monoclinic, plastic and rhombic.
Rhombic sulphur exists at ordinary temperature and is also know as alpha sulphur. Rhombic sulphur exists as crown shaped S8 rings and has a density of 2.06 .

When rhombic sulphur is heated gently and allowed to cool down, long needle like crystals are formed which is known as monoclinic sulphur. It is also called Beta sulphur. These crystals are almost colourless . Monoclinic sulphur also exists as crown shaped S8 rings and has a density of 1.96 .Plastic sulphur is formed by heating rhombic sulphur at high temperature. It is orange in colour .It is also known as lambhda sulphur.

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