Key Points
Key Points: Group 16 Elements - The Oxygen Family
General electronic configuration: ns² np⁴
| Element | Symbol | Configuration |
|---|---|---|
| Oxygen | O | [He] 2s² 2p⁴ |
| Sulphur | S | [Ne] 3s² 3p⁴ |
| Selenium | Se | [Ar] 3d¹⁰ 4s² 4p⁴ |
| Tellurium | Te | [Kr] 4d¹⁰ 5s² 5p⁴ |
| Polonium | Po | [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁴ |
- General Trends: Down the group → atomic size increases, while electronegativity and ionisation energy decrease.
- Oxidation States: Common states → −2, +2, +4, +6 (oxygen mainly −2; heavier elements show positive states).
- Chemical Reactivity: Decreases down the group → O > S > Se > Te > Po.
Hydrides Trend (H₂E):
- Bond angle decreases: H₂O > H₂S > H₂Se > H₂Te
- Thermal stability decreases down the group
- Acidic character increases: H₂O < H₂S < H₂Se < H₂Te
Sulphur Allotropes:
- Rhombic (α): Most stable, prepared from CS₂ solution
- Monoclinic (β): Formed by melting sulphur
Both consist of S₈ ring structure
Important Compounds & Reactions:
- H₂S: Poisonous, reducing agent
- SO₂: Acts as reducing + oxidising + bleaching agent
- O₃ (Ozone): Strong oxidising agent; converts KI → KIO₃/KIO₄
- O₂/O₃: Show allotropy
Sulphuric Acid (H₂SO₄):
- Dibasic acid
- Strong dehydrating agent
- Strong oxidising agent
- Low volatility & highly corrosive
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]
- Explain the Trends in the Following Properties with Reference to Group 16
- Explain the Following Properties of Group 16 Elements
- Explain anomalous behaviour of oxygen in group 16 with respect to: Atomicity Magnetic property Oxidation state
- Describe anomalous behaviour of oxygen as compared with other elements of group 16 with reference to
- Write two uses of dioxygen.
- What is the Action of Dioxygen on Calcium
- What is the Action of Dioxygen On Carbon Disulfide
- What is the Action of Dioxygen On Iron
- What Are Neutral Oxides?
- Explain the Nature of Zinc Oxide with the Help of the Reactions.
- The Binary Compounds of Oxygen with Other Elements Are Called Oxides.
- Write the Electronic Configuration of the Following Elements: Sulphur (Z = 16)
- The Atomicity of Sulphur in Orthorhombic Sulphur is
- 3.795 G of Sulphur is Dissolved in 100g of Cs2. this Solution Boils at 319.81 K. What is the Molecular Formula of Sulphur in Solution
- Which of the following compounds contain S = O as well as S = S bonds?
- H2O is liquid while H2S is gas at room temperature. Explain.
- Write the molecular and structural formulae of thiosulfuric acid.
- Explain the Structure of Sulphur Dioxide.
- Write the chemical equation for the preparation of sulphur dioxide from sulphur.
- What is Molecular Formula of Oleum?
- What is the Action of Concentrated Sulphuric Acid on Copper
- What is the Action of Concentrated Sulphuric Acid On Potassium Chlorate?
- What Happens When Dilute Sulphuric Acid is Treated with Fe
- What Happens When Dilute Sulphuric Acid is Treated With Caf2 Calcium Fluoride,
- Write Chemical Reactions for Different Steps in the Manufacture of Sulphuric Acid by Lead Chamber Process. Draw the Structure of Phosphorous Pentachloride
- Write Structure and Molecular Formula for the Following Compounds: A. Orthophosphoric Acid B. Sulphurous Acid
- Write the Formula for Pentaamminechlorocobalt (Iii) Sulphate.
- Draw the structure of the following: H2SO4
- What is the Action of Concentrated Sulphuric Acid on Phosphorous Pentachloride
- The molecular formula H2S2O2 represents which oxoacid?
- Write uses of sulphur.
- Write the molecular formula and structures of the peroxy monosulphuric acid.
- Write Molecular Formulae and Structures of the Dithionous Acid
- Write the Molecular and Structural Formulae Of Dithionous Acid
- Write molecular formula and structure of Pyrosulphuric acid
- Write the molecular formula and structure of dithionic acid.
