Lecture 7: D and F Block Elements

Jun 10, 2024

Lecture 7 of D and F Block Elements

Introduction

  • Welcome to Physics Wallah's lecture 7 on D and F block elements.
  • Ensure to solve and review all provided lectures, questions, and DPPS for high marks.
  • Lecture focus: Potassium permanganate and F block elements.

Review from Last Lecture

  • Previous topics: Dioxides, Potassium Dichromate.
  • Importance of thorough understanding and solving DPPS.
  • Potassium Dichromate: Vital lab chemical, often recurring in exams.

Current Lecture: Potassium Permanganate (KMnO4)

Appearance

  • KMnO4: Purple crystal, KMnO4 formula.
  • Common use in titrations (oxidizing agent).

Preparation Methods

1. Commercial Method

  • Alkaline oxidative fusion of MnO2.
  • Reaction with KOH and O2:
    • MnO2 + KOH + O2 → K2MnO4 + H2O
  • Manganate (green), converted to Permanganate by electrolysis or chemical oxidation.
  • Reaction with KNO3 and other oxidizing agents.

2. Electrolytic Oxidation

  • K2MnO4 electrolysis gives KMnO4 and other products.
  • Reaction formula: MnO42- + H2O → MnO4- + MnO2.

Properties

  1. Color: Dark purple, needle-like crystalline solid with metallic luster.
  2. Decomposition: Decomposes at 513K.
  3. Oxidizing Agent: Strong oxidizing in acidic, neutral, and alkaline mediums.
    • Acidic: MnO4- + 8H+ + 5e- → Mn2+ + 4H2O
    • Basic: MnO4- + e- → MnO42-
    • Neutral: MnO4- + 2H2O + 3e- → MnO4- + MnO2 + 4OH-

Uses

  1. Analytical chemistry (lab use).
  2. Bleaching agent.
  3. Decontaminating water.
  4. Organic synthesis applications.
  5. Oxidizing agent in various reactions (e.g., with NO2-, C2O4 2-, Br-).

Introduction to F-Block Elements

General Information

  • Position: Bottom of the periodic table.
  • Split into lanthanoids (4f-series) and actinoids (5f-series).
  • Named based on the last electron entering the 'f' subshell.
  • Classified as inner transition elements.

Lanthanoids

  • Period 6, group 3 of periodic table.
  • Elements 58 (Ce) to 71 (Lu).
  • General electron configuration: [Xe] 4f^1-14 5d^0-1 6s^2.
  • F-electrons fill antispenultimate shell.

Actinoids

  • Period 7, group 3 of periodic table.
  • Elements 90 (Th) to 103 (Lr).
  • General electron configuration: [Rn] 5f^1-14 6d^0-1 7s^2.
  • Filling of 5f sub-shell.

Electronic Configurations of Lanthanoids

  • La: [Xe] 5d^1 6s^2
  • Ce: [Xe] 4f^1 5d^1 6s^2
  • Pr: [Xe] 4f^3 6s^2
  • Nd: [Xe] 4f^4 6s^2
  • Sm: [Xe] 4f^6 6s^2
  • Eu: [Xe] 4f^7 6s^2
  • Gd: [Xe] 4f^7 5d^1 6s^2
  • Tb: [Xe] 4f^9 6s^2
  • Dy: [Xe] 4f^10 6s^2
  • Ho: [Xe] 4f^11 6s^2
  • Er: [Xe] 4f^12 6s^2
  • Tm: [Xe] 4f^13 6s^2
  • Yb: [Xe] 4f^14 6s^2
  • Lu: [Xe] 4f^14 5d^1 6s^2

Lanthanoid Contraction

  • Trend: Decrease in size from Ce to Lu.
  • Due to poor shielding effect of 4f electrons.
  • Consequences:
    • Similarity in ionic radii of 4d and 5d block elements.
    • Difficulty in separation of lanthanoids.
    • Affect on atomic size across periods.
    • Higher nuclear charge results in smaller ionic radii.

Quiz and Homework

  • Revise and memorize the electronic configurations and properties discussed.
  • Solve given problems on Lanthanoid Contraction and properties of KMnO4.

Conclusion

  • Finish review of lanthanoid series in next class.
  • Preview of next chapter: Coordination Compounds.
  • Emphasis on regular study and daily problem solving.