1. Transition Elements and Oxidation States
a) Transition elements show variable oxidation states because in these elements, d and s electrons have comparable energies, allowing both to participate in chemical reactions.
b) The two types of magnetic behavior are diamagnetism and paramagnetism.
2. Magnetic Moment of Sc³⁺
The valence shell electronic configuration of Sc³⁺ ion is 3d⁰, so the number of unpaired electrons (n) = 0.
Magnetic moment, µₛ = √n(n+2) = √0(0+2) = 0.
The observed magnetic moment agrees with the calculated value.
3. Lanthanide Ions: Unpaired Electrons and Properties
Given ions: La³⁺, Ce⁴⁺, Yb²⁺, Lu³⁺ (Atomic numbers: La=57, Ce=58, Yb=70, Lu=71)
a) Number of unpaired electrons:
-
La³⁺: 4f⁰ → 0
-
Ce⁴⁺: 4f⁰ → 0
-
Yb²⁺: 4f¹⁴ → 0
-
Lu³⁺: 4f¹⁴ → 0
b) All ions are diamagnetic.
c) All ions are colorless because they lack partially filled orbitals.
4. Potassium Permanganate as an Oxidizing Agent
a)
i) Alkaline/neutral medium:
2MnO₄⁻ + H₂O + I⁻ → 2MnO₂ + 2OH⁻ + IO₃⁻
ii) Acidic medium:
10I⁻ + 2MnO₄⁻ + 16H⁺ → 5I₂ + 2Mn²⁺ + 8H₂O
b)
i) With K₂Cr₂O₇:
6I⁻ + Cr₂O₇²⁻ + 14H⁺ → 3I₂ + 2Cr³⁺ + 7H₂O
ii) Baeyer’s reagent: Alkaline KMnO₄ solution.
5. Oxidizing Agents: KMnO₄ and K₂Cr₂O₇
a) Ores:
-
KMnO₄: Pyrolusite (MnO₂)
-
K₂Cr₂O₇: Chromite ore (FeCr₂O₄)
b) Reactions in acidic medium:
-
KMnO₄: 10I⁻ + 2MnO₄⁻ + 16H⁺ → 5I₂ + 2Mn²⁺ + 8H₂O
-
K₂Cr₂O₇: 6I⁻ + Cr₂O₇²⁻ + 14H⁺ → 3I₂ + 2Cr³⁺ + 7H₂O
6. Heating KMnO₄ Crystals
Products: K₂MnO₄, MnO₂, and O₂
Equation: 2KMnO₄ → K₂MnO₄ + MnO₂ + O₂
7. Properties of Transition and f-Block Elements
a) Properties of transition elements:
-
Variable oxidation states
-
Formation of colored compounds
-
Paramagnetism
-
Catalytic activity
b)
i) Common oxidation state of lanthanoids: +3
ii) Lanthanoid with +4 state: Cerium (Ce)
iii) Separation difficulty: Due to lanthanoid contraction, they have similar radii and properties.
8. Atomic Size and Electrode Potential
a) Zr and Hf have similar sizes due to lanthanoid contraction.
b) Exceptions in E⁰ values (Ni/Ni²⁺ and Zn/Zn²⁺) are due to high negative hydration enthalpy and stable electronic configurations.
9. Transition Elements: Key Points
a) Zn is not a transition element because it lacks partially filled d orbitals.
b) Fe³⁺ is more paramagnetic than Fe²⁺.
c) Variable oxidation states arise from d and s electron participation.
d) Catalytic activity is due to surface area and variable oxidation states.
10. Preparation of K₂Cr₂O₇ from Chromite Ore
-
Fusion:
4FeCr₂O₄ + 8Na₂CO₃ + 7O₂ → 8Na₂CrO₄ + 2Fe₂O₃ + 8CO₂ -
Acidification:
2Na₂CrO₄ + 2H⁺ → Na₂Cr₂O₇ + 2Na⁺ + H₂O -
Conversion:
Na₂Cr₂O₇ + 2KCl → K₂Cr₂O₇ + 2NaCl
Consequence of lanthanoid contraction: Similar radii in 2nd and 3rd transition series.
11. Seminar on Transition Elements
Properties:
-
Variable oxidation states
-
Magnetic properties
-
Colored compounds
-
Catalytic activity
12. Trends in Atomic/Ionic Radii
a) Decrease across a series due to increased nuclear charge.
b) 4d elements are larger than 3d due to more shells.
c) Similar radii in 4d and 5d due to lanthanoid contraction.
13. d-Block Elements
a) Common oxidation state: +2
b) Important compounds: K₂Cr₂O₇, KMnO₄
c) Complex formation due to small size, high charge, and vacant d orbitals
d) Misch metal: Alloy of lanthanoids and iron
14. K₂Cr₂O₇: Preparation and Color
Color arises from charge transfer spectrum.
15. Transition Metal Compounds
a) See properties in question 7
b) Uses of KMnO₄: Oxidizing agent, titrations
c) Structure of Cr₂O₇²⁻: Two tetrahedral CrO₄ units sharing an oxygen atom
16. Lanthanoid Contraction and KMnO₄ Preparation
a) Lanthanoid contraction: Gradual decrease in radii due to poor f-orbital shielding
b) KMnO₄ from MnO₂:
-
2MnO₂ + 4KOH + O₂ → 2K₂MnO₄ + 2H₂O
-
Electrolysis: MnO₄²⁻ → MnO₄⁻
17. Lanthanoids and Transition Series
a) Oxidation state: +3
b) Structures:
-
CrO₄²⁻: Tetrahedral
-
Cr₂O₇²⁻: Two tetrahedra sharing an oxygen
c) Zr and Hf: Similar due to lanthanoid contraction
18. Manganese Oxidation States and KMnO₄
a) Mn does not show +1 state
b) Cr₂O₇²⁻ structure: See question 15
c) KMnO₄ + Fe²⁺:
5Fe²⁺ + MnO₄⁻ + 8H⁺ → 5Fe³⁺ + Mn²⁺ + 4H₂O
19. Transition and f-Block Elements
i) See properties in question 7
ii) KMnO₄ is an oxidizing agent
iii) Lanthanoid contraction: Decreasing radii across lanthanoids
iv) Consequences: Similar radii, difficult separation
20. Transition Elements and Lanthanoids
a)
i) See properties in question 7
ii) Cr²⁺ (reducing) → Cr³⁺ (stable d³); Mn³⁺ (oxidizing) → Mn²⁺ (stable d⁵)
b) Non-lanthanoid: Thorium
21. Magnetic Moments and Color
a) Zr and Hf: Similar due to lanthanoid contraction
b) Magnetic moments:
-
Sc³⁺: 0
-
Ti³⁺: 1.73 BM
c) Color: Due to partially filled d orbitals
22. Structure of CrO₄²⁻
Tetrahedral
23. Transition Elements: Catalysts and Scandium
a) Catalytic activity due to surface area and oxidation states
b) Scandium is a transition element (partially filled d orbitals)
c) Preparation of Na₂CrO₄:
4FeCr₂O₄ + 8Na₂CO₃ + 7O₂ → 8Na₂CrO₄ + 2Fe₂O₃ + 8CO₂
24. Magnetic Moment of d¹⁰ Configuration
Zero (no unpaired electrons)
25. Lanthanoid Contraction and Consequences
Definition: Gradual decrease in radii due to poor f-orbital shielding
Consequences: Similar radii, difficult separation
26. Disproportionation of MnO₄²⁻
Forms MnO₄⁻ and MnO₂
27. Applications of d/f-Block Elements
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Catalysts (e.g. Fe in Haber process)
-
Alloys
-
Batteries (Zn, Ni, MnO₂)
28. Maximum Oxidation States in 3d Series
Manganese (+2 to +7)
29. Lanthanoid Contraction
Due to poor f-electron shielding and increasing nuclear charge
30. d-Block Trends and Magnetic Moment
a) Similar radii in 2nd and 3rd series: Lanthanoid contraction
b) Cu²⁺ (3d⁹): µₛ = 1.73 BM
32. Lanthanoid Oxidation States and Atomic Sizes
a) +3 oxidation state
b) Zr and Hf: Similar due to lanthanoid contraction
33. Oxidation States and Magnetic Behavior
a) Variable due to d and s electron participation
b) Diamagnetism and paramagnetism
c) M²⁺ (Z=27, 3d⁷): µₛ = 3.87 BM
34. Potassium Dichromate Preparation
i) Ore: Chromite (FeCr₂O₄)
ii) Steps:
-
2Na₂CrO₄ + 2H⁺ → Na₂Cr₂O₇ + 2Na⁺ + H₂O
-
Na₂Cr₂O₇ + 2KCl → K₂Cr₂O₇ + 2NaCl
35. Transition Metals as Catalysts
i)
A. Zr and Hf: Lanthanoid contraction
B. Catalytic property: Surface area, oxidation states
ii) M²⁺ (Z=27, 3d⁷): µₛ = 3.87 BM
39. Cr²⁺ vs. Mn³⁺
Cr²⁺ → Cr³⁺ (stable d³); Mn³⁺ → Mn²⁺ (stable d⁵)
40. Zr and Hf Similarity
Due to lanthanoid contraction
42. Completely Filled d Orbital
Ag (4d¹⁰5s¹)
43. Variable Oxidation States and 3d Maximum
i) Due to d and s electron participation
ii) Manganese shows maximum oxidation states
45. Oxidation Number of Mn in KMnO₄
+7
48. Colored Transition Metal Ions
i) Ti³⁺ (3d¹), Cr³⁺ (3d³)
ii) Color: Due to d-d transitions
49. Lanthanoid Contraction and Consequences
See question 16
50. Similar Radii in Transition Series
i) Lanthanoid contraction
ii) See question 16
51. Alloys and Lanthanoids
i) Alloys are solid solutions with metals
ii) Example: Misch metal (Ln + Fe)
iii) Use: Bullets, lighter flints