GENERAL PROPERTIES OF THE SULPHUR GROUP (GROUP VI ELEMENTS)
The group VI elements include: Oxygen, Sulphur, Selenium, Tellurium and Polonium.
Table of Contents
- Metallic property increases down the group. Oxygen and sulphur are non-metal; selenium and tellurium are metalloid; while polonium is a metal.
- All the elements are solid except oxygen which is a gas at room temperature.
- Oxygen and sulphur exhibit allotropy.
- They have six electrons in their outermost shell. Hence their oxidation number is -2; though sulphur can exhibit -4 and -6 states in some compounds.
- Electronegativity decreases down the group. Thus, oxygen is a good oxidizing agent.
ELECTRONIC STRUCRURE OF SULPHUR GROUP
Members of the sulphur family include: Oxygen, Sulphur, Selenium, Tellurium and Polonium. Their electronic configurations are shown below:
Oxygen = 8: 1s2 2s2 2p4
Sulphur = 16: 1s2 2s2 2p6 3s2 3p4
Selenium= 34: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p4
Tellurium = 52: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p4
Polonium = 84: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 5d10 5f14 6s2 6p4
Sulphur is an element. It occurs freely as deposits and in combined state as sulphide and as tetraoxosulphate (IV).
EXTRACTION OF SULPHUR
Sulphur is extracted from underground by Frasch process. A three concentric sulphur pump is driven down a hole dug to the sulphur bed. The solid sulphur is melted at 115oC by super – heated water at 170oC and 10atms. The molten sulphur is forced out by hot compressed air at 15atm. The molten sulphur is then continuously pumped out and allowed to solidify in a large tank. The sulphur obtained is 99.5% pure.
ALLOTROPES OF SULPHUR
The two main crystalline allotropes of sulphur are:
- Rhombic sulphur: A bright yellow octahedral crystalline solid. Each crystal is made up of S8 Rhombic sulphur is stable below 96oC.
- Monoclinic Sulphur: This is amber coloured solid sulphur consisting of needle shaped S8 Stable above 96oC. It easily reverts to Rhombic below 96oC. The transition temperature between Rhombic and Monoclinic is 96oC.
Comparison of the Physical Properties of Rhombic and Monoclinic Sulphur
- Rhombic Sulphur melts at 113oC;while monoclinic sulphur melts at 119o
- Rhombic sulphur has bright yellow colour; while monoclinic sulphur has amber colour.
- Rhombic sulphur has octahedral shape; while monoclinic sulphur is needle-like in shape.
- Rhombic sulphur is translucent; while monoclinic is transparent.
Sulphur also exists as non – crystalline solid. These are
- Amorphous sulphur
- Plastic sulphur
- Briefly explain the Frasch process.
- Name the two allotropes of sulphur and state their transition temperature.
- Sulphur is a yellow solid.
- It is insoluble in water but soluble in toluene and carbon (IV) sulphide.
- It is a poor – conductor of heat and electricity.
- It melts at 119oC and boils at 444o
- It reacts directly with metals to form sulphide (S2-)
Fe(s) + S(s) → FeS(s)
- It reacts with excess oxygen to form sulphur (IV) oxide
O2(g) + S(s) → SO2(g)
- It reacts with hydrogen to form hydrogen sulphide;
H2(g) + S(s) → H2S(g)
- It reacts with coke (carbon) to form carbon (IV) sulphide.
C(s) + 2S(s) → CS2(l)
USES OF SULPHUR
- Used in manufacturing tetraoxosulphate (IV) acid
- Used in vulcanization of rubber
- Used as germicides
- Used in manufacturing bleaching agent
- State THREE physical and chemical properties of sulphur.
- Outline THREE differences between monoclinic and rhombic sulphur.
- Descried the Frasch process for the extraction of sulphur.
- State TWO differences between a conductor and an electrolyte.
- List the steps involve in the treatment of water for municipal supply.
SECTION A: Write the correct option ONLY
- Sulphur is extracted by (a) Haber process (b) Frasch process (c) Solvay process (d) Contact process
- Which of the following is a crystalline allotropes of sulphur (a) Monoclinic (b) Plastic (c) Amorphous (d) Colloidal
- The density of rhombic sulphur is (a) 1.2 (b) 1.5 (c) 2.08 (d) 1.98
- The shape of monoclinic sulphur is (a) needle shape (b) hexagonal (c) octahedral (d) tetrahedral
- Sulphur is used for (a) making of cellulose (b) cooking rice (c) vulcanizing rubber (d) manufacturing glass
- Give three differences between rhombic sulphur and monoclinic sulphur
- Briefly describe the extraction of sulphur