Key Points
Key Points: Group 15 Elements - The Nitrogen Family
General electronic configuration: ns² np³
| Element | Symbol | Configuration |
|---|---|---|
| Nitrogen | N | [He] 2s² 2p³ |
| Phosphorus | P | [Ne] 3s² 3p³ |
| Arsenic | As | [Ar] 3d¹⁰ 4s² 4p³ |
| Antimony | Sb | [Kr] 4d¹⁰ 5s² 5p³ |
| Bismuth | Bi | [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p³ |
- General Trends: Down the group → atomic size, density, boiling point increase, while ionisation enthalpy decreases.
- Melting Point Trend: Increases from N → As, then decreases from As → Bi.
- Electron Gain Enthalpy: Generally increases down the group (becomes more negative).
- Oxidation States: Show −3, +3, +5 → +5 stability decreases down the group due to the inert pair effect.
Important Compounds/Exceptions:
- PCl₅ exists as ionic solid → [PCl4]+[PCl6]−
- NF₃ is stable, while other trihalides are unstable
- Bond strength: PCl₃ > AsCl₃ > SbCl₃
Special Reactions:
- PH₃ is not spontaneously inflammable (unlike impure phosphine)
- With AgNO₃: forms Ag₃P (black ppt)
- With NH₃: forms (NH₄)₂PtCl₆ (yellow ppt)
Phosphorus Allotropes:
- White P: Reactive, glows in the dark (chemiluminescence), soluble in CS₂
- Red P: Stable, no glow
- Black P: Most stable, highest density, polymeric
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: 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 |
Key Points: Group 17 Elements - The Halogen Family
General electronic configuration: ns² np⁵
| Element | Symbol | Configuration |
|---|---|---|
| Fluorine | F | [He] 2s² 2p⁵ |
| Chlorine | Cl | [Ne] 3s² 3p⁵ |
| Bromine | Br | [Ar] 3d¹⁰ 4s² 4p⁵ |
| Iodine | I | [Kr] 4d¹⁰ 5s² 5p⁵ |
| Astatine | At | [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵ |
Trends in Different Properties:
| Property | Trend |
|---|---|
| Enthalpy of Dissociation | Cl₂ > Br₂ > F₂ > I₂ |
| Dipole Moment | HF > HCl > HBr > HI |
| Ionic Character | HI < HBr < HCl < HF |
| Bond Length | HF < HCl < HBr < HI |
| Bond Strength | HI < HBr < HCl < HF |
| Thermal Stability | HI < HBr < HCl < HF |
| Reducing Power | HF < HCl < HBr < HI |
| Acid Strength | HF < HCl < HBr < HI |
Key Points: Oxoacids of Halogens
| Oxidation state of X | Generic name | Oxoacids of fluorine | Oxoacids of chlorine | Oxoacids of bromine | Oxoacids of iodine |
|---|---|---|---|---|---|
| +1 | Hypohalous acid (HXO) | HOF | HOCl | HOBr | HOI |
| +3 | Halous acid (HXO₂) | – | HOClO | – | – |
| +5 | Halic acid (HXO₃) | – | HOClO₂ | HOBrO₂ | HOIO₂ |
| +7 | Perhalic acid (HXO₄) | – | HOClO₃ | HOBrO₃ | HOIO₃ |
Key Points: Interhalogen Compounds
Types of Interhalogen Compounds:
| Type | Examples |
|---|---|
| XX′ | ClF, BrF, ICl, IBr |
| XX′₃ | ClF₃, BrF₃, IF₃ |
| XX′₅ | ClF₅, BrF₅, IF₅ |
| XX′₇ | IF₇ |
Methods of Preparation:
| Method | Reactions |
|---|---|
| Direct combination | Cl₂ + F₂ → 2ClF Br₂ + 3F₂ → 2BrF₃ I₂ + 3Cl₂ → 2ICl₃ |
| Halogen + interhalogen | Br₂ + BrF₃ → 3BrF Br₂ + ClF₃ → 2BrF₃ + BrCl |
| Special (ICl) | I₂ + KClO₃ → ICl + KIO₃ |
Key Points: Group 18 Elements - The Noble gas Family
Electronic Configurations:
- General electronic configuration: ns² np⁶ (He = 1s²)
- Elements: He, Ne, Ar, Kr, Xe, Rn
- Noble gases have very high ionisation enthalpies and positive electron gain enthalpies — so they generally do not form compounds.
- First noble gas compound prepared by Neil Bartlett: \[\mathrm{O}_{2}(\mathrm{g})+\mathrm{PtF}_{6}(\mathrm{g})\longrightarrow\mathrm{O}_{2}^{+}[\mathrm{PtF}_{6}]^{-}(\mathrm{s})\] — since the ionisation enthalpy of Xe ≈ that of O₂, Xe was reacted similarly.
Shapes and Hybridisation of Xenon Compounds:
| Molecule | Hybridisation | Geometry | Shape |
|---|---|---|---|
| XeO₃ | sp³ | Tetrahedral | Pyramidal |
| XeO₄ | sp³ | Tetrahedral | Tetrahedral |
| XeOF₂ | sp³d | Trigonal bipyramidal | T-shaped |
| XeOF₄ | sp³d² | Octahedral | Square pyramidal |
| XeO₂F₂ | sp³d | Trigonal bipyramidal | Distorted trigonal bipyramidal (see-saw) |
| XeO₃F₂ | sp³d | Trigonal bipyramidal | Trigonal bipyramidal |
| XeO₃F₄ | sp³d² | Octahedral | Octahedral |
Important Questions [109]
- Account for the Following : Nitrogen Does Not Form Pentahalide.
- What Happens When (Nh4)2cr2o7 is Heated? Write the Equations.
- Pb(No3)2 on Heating Gives a Brown Gas Which Undergoes Dimerisation on Cooling? Identify the Gas
- Why does NO2 dimerise?
- Tendency to Show –3 Oxidation State Decrease from Nitrogn (N) to Bismuth (Bi).
- Write the Name of Gas Released When Cu is Added to Conc. Hno3
- Write the Name of Gas Released When Cu is Added to Dilute Hno3
- Which Allotrope of Sulphur is Thermally Stable at Room Temperature ?
- Give reason for the following: Red phosphorus is less reactive than white phosphorus.
- Answer the Following Question. Write the Disproportionation Reaction of H3po3.
- Which allotrope of phosphorus is more reactive and why?
- Out of White Phosphorus and Red Phosphorus, Which One is More Reactive and Why?
- Draw the structures of the following molecules: (HPO3)3
- What happens when H3PO3 is heated?
- which poisonous gas is evolved when white phosphorus is heated with conc. NaOH solution? Write the chemical equation involved
- Complete the following chemical equation: Ca3P2+H2O ->
- Account for the Following : Solid PCl5 is Ionic in Nature.
- Complete and balance the following equation: PCl3 + H2O ->
- Complete the Following Equations: Ag+PCl5 →
- What is the Basicity of H3po3 ?
- Write Balanced Chemical Equations Involved in the Following Reactions: Calcium Phosphide is Dissolved in Water.
- Draw the Structures of the Following: H4p2o7 (Pyrophosphoric Acid)
- What is the basicity of H3PO4?
- Give reasons for the following : H3PO2 is a stronger reducing agent than H3PO3.
- Complete the following equations : P4 + H2O →
- Give reasons: SO2 is reducing while TeO2 is an oxidising agent.
- Give Reactions for the Following: O – O Single Bond is Weaker than S – S Single Bond.
- Account for the Following: Oxygen Shows Catenation Behavior Less than Sulphur.
- Give Reasons for the Following : H2Te is the Strongest Reducing Agent Amongst All the Hydrides of Group 16 Elements.
- Account for the Following : There is Large Difference Between the Melting and Boiling Points of Oxygen and Sulphur.
- Arrange the following in order of the property indicated set. HF, HCl, HBr, HI-decreasing bond enthalpy
- Give Reasons for the Following : Oxygen Has Less Electron Gain Enthalpy with Negative Sign than Sulphur.
- Arrange the Following in the Order of the Property Indicated Against Set : H2o, H2s, H2se, H2te − Increasing Acidic Character.
- Draw the Structures of `H3po2`
- Give Reasons Thermal Stability Decreases from H2o to H2te
- Write the Formula of the Compound of Iodine Which is Obtained When Conc. Hno3 Oxidises I2
- Give Reasons for the Following: N2o5 is More Acidic than N2o3
- How Do You Prepare: K2mno4 from Mno2?
- The Two O−O Bond Lengths in the Ozone Molecule Are Equal.
- Give Reasons for the Following: Ozone is Thermodynamically Less Stable than Oxygen.
- Give a Reason for the Following : Ozone is Thermodynamically Less Stable than Oxygen.
- Complete the equation PbS + O3 gives
- How the Supersonic Jet Aeroplanes Are Responsible for the Depletion of Ozone Layers?
- Account for the following : Ozone is thermodynamically unstable
- Give reasons for the following: Sulphur in vapour state shows paramagnetic behaviour.
- Give Reasons Dioxygen is a Gas While Sulphur is a Solid at Room Temperature.
- How Do You Prepare: Na2cr2o7 from Na2cro4?
- What Happens When So3 Is Passed Through Water? Write the Equations.
- What Happens When Conc. is H2so4 Added to Cu? Write the Equations.
- Draw the Structures of the Following : H2s2o7
- Draw the structure of the following: H2S2O7
- Answer the Following Question. Write a Chemical Reaction to Test Sulphur Dioxide Gas. Write a Chemical Equation Involved.
- What happens when: SO2 gas is passed through an aqueous solution Fe+3 salt?
- Write the structures of the following molecule: H2SO3
- Draw the Structures of the Following Molecules: H2S2O8
- Account for the Following : H3po2 Is a Stronger Reducing Agent than H3po3.
- Draw Structures of the Following:
- Write One Difference Between Transition Elements and P-block Elements with Reference to Variability of Oxidation States.
- Write the conditions to maximize the yield of H2SO4 by contact process.
- Complete the following equations: C + conc. H2SO4 →
- Complete the following equations: CaF2+H2SO4 →
- Complete and Balance the Following Equations: S+H2so4(Conc.) →
- Draw the structure of the following: H2SO4
- When Concentrated Sulphuric Acid Was Added to an Unknown Salt Present in a Test Tube a Brown Gas (A) Was Evolved Identify (A) and (B).And Write the Structures of (A) and (B). and Why Does Gas (A) Change to Solid on Cooling?
- Cl2 Acts as a Bleaching Agent.
- Complete Chemical Reactions Are:Cl2 + H2o → [Hcl + Hocl] →2 Hcl + [O] (Nascent Oxygen)
- Account for the Following : Acidic Character Increases from HF to HI.
- Complete the Following Equations: Kmno4
- F2 has lower bond dissociation enthalpy than Cl2. Why?
- Which halogen compound in the following pair will react faster in SN2 reaction CH3Br or CH3I.
- Which halogen compound in each of the following pairs will react faster in SN2 reaction (CH3)3 C – Cl or CH3 – Cl
- Account for the Following: Fluorine Does Not Exhibit Positive Oxidation State.
- Compare the Oxidizing Action of F2 and Cl2 by Considering Parameters Such as Bond Dissociation Enthalpy, Electron Gain Enthalpy and Hydration Enthalpy.
- Arrange the Following in the Decreasing Order of Their Reducing Character : Hf, Hcl, Hbr, Hi
- Fluorine is a Stronger Oxidising Agent than Chlorine. Why?
- Write Balanced Chemical Equations Involved in the Following Reactions:
- Out of Chlorobenzene and Benzyl Chloride, Which One Gets Easily Hydrolysed by Aqueous Naoh and Why?
- Give Reasons for the Following: Electron Gain Enthalpies of Halogens Are Largely Negative.
- Write the Structure of the Product When Chlorobenzene is Treated with Methyl Chloride in the Presence of Sodium Metal and Dry Ether.
- Write the Structure of the Alkene Formed by Dehydrohalogenation of 1-bromo-1methylcyclohexane with Alcoholic Koh.
- What happens when (i) PCl5 is heated ? Write the reactions involved.
- Draw the structures of the HClO3.
- Draw the Structures of the Following: (1)Hclo4 (2)H3po3
- Account for the following: Fluorine forms only one oxoacid HOF.
- Account for the Following : Hclo4 is a Stronger Acid than Hclo.
- ICl is more reactive than I2.
- Draw the structure of BrF5
- Draw the Structures of the Following: Brf5
- Account for the Following: Interhalogens Are More Reactive than Pure Halogens.
- Draw the structures of the following : ClF3
- Draw the structures of the following molecules: BrF3
- Complete the equation : XeF2+PF5 →
- Draw the Structures of the Following Xef6
- Draw the structure of the following molecule: XeF4
- Write the structures of the following molecule: XeOF4
- Draw the Structures of the Following Molecules: Xef2
- Complete the following equation: XeF𝐴2+H𝐴2O
- Draw the Structure of Xef4.
- Complete the following equations : XeF4 + O2F2→
- Draw the structure of the following: XeO3
- Complete the Following Reactions : Xef6 + 3h2o →
- Complete the Given Chemical Equations: 2xef_2 + 2h_2o->
- Complete the Following Reactions: Xef6+2h2o ----->
- Which noble gas has the lowest boiling point?
- Which noble gas is used in filling balloons for meteorological observations?
- Account for the following: Helium is used in diving apparatus.
- What happens when: XeF4 reacts with SbF5?
- Draw Structures of the Following: Xef4
- Account for the Following : Although Fluorine Has Less Negative Electron Gain Enthalpy Yet F2 is a Strong Oxidizing Agent.
Concepts [28]
- Group 15 Elements - The Nitrogen Family
- Dinitrogen
- Ammonia
- Oxides of Nitrogen
- Nitric Acid
- Phosphorus - Allotropic Forms
- Compounds of Phosphorus
- Phosphine
- Phosphorus Halides
- Oxoacids of Phosphorus
- Group 16 Elements - The Oxygen Family
- Dioxygen
- Classification of Oxides
- Simple Oxides
- Ozone
- Sulphur - Allotropic Forms
- Compounds of Sulphur
- Sulphur Dioxide
- Oxoacids of Sulphur
- Sulphuric Acid
- Group 17 Elements - The Halogen Family
- Compounds of Halogens
- Chlorine
- Hydrogen Chloride
- Oxoacids of Halogens
- Interhalogen Compounds
- Group 18 Elements - The Noble gas Family
- P Block Elements
