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Revision: P-block Elements >> Group 16 Elements Chemistry HSC Science (General) 12th Standard Board Exam Maharashtra State Board

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Key Points

Key Points: Anomalous Behaviour of Oxygen

Reasons

  • Small atomic size
  • High electronegativity and ionisation energy
  • Absence of d-orbitals

Important Properties

Property Oxygen
Nature Diatomic gas (O₂)
Magnetic behaviour Paramagnetic
Oxidation state Mainly −2
Hydride H₂O is liquid at room temperature
Covalency Usually 2
Key Points: Sulphur - Allotropic Forms

Allotropes of Sulphur:

Property Rhombic (α) Monoclinic (β)
Colour Pale yellow Bright yellow
Shape Orthorhombic Needle-shaped
Melting point 385.8 K 393 K
Density 2.06 g/cm³ 1.98 g/cm³
Stability Stable below 369 K Stable above 369 K
Solubility Insoluble in water, soluble in CS₂ Soluble in CS₂

Allotropes of Group 16:

Element Allotropes
Oxygen O₂, O₃ (ozone)
Sulfur Rhombic, Monoclinic
Selenium Red (non-metallic), Grey (metallic)
Tellurium Crystalline, Amorphous
Polonium α and β (both metallic)
Key Points: Compounds of Sulphur
Property SO₂ (Sulphur dioxide) H₂SO₄ (Sulphuric acid)
Preparation FeS₂ + O₂ → SO₂ Contact process
Physical Colourless, pungent, poisonous gas Colourless, dense, oily liquid
Nature Reducing agent Strong acid
Key reactions With O₂ → SO₃ (V₂O₅) Dehydrating agent
Special reaction Decolourises KMnO₄ Sugar → carbon
Other reactions With NaOH → Na₂SO₃ With salts → HCl
Uses Bleaching, disinfectant Fertilisers, industry
Key Points: Oxoacids of Sulphur
Name Formula
Sulfurous acid H₂SO₃
Sulfuric acid H₂SO₄
Disulfuric (Pyrosulfuric) acid H₂S₂O₇
Peroxomonosulfuric acid H₂SO₅
Peroxodisulfuric acid H₂S₂O₈
Thiosulfuric acid H₂S₂O₃

Important Questions [36]

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