Exam Master Review Sheet - d & f Block Elements

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EXAM MASTER REVIEW SHEET

d and f Block Elements

High-Yield Synthesis for JEE Main, Advanced & NEET

1. Transition Elements (d-block)

General Config.

\[ (n-1)d^{1-10} ns^{1-2} \]

*Zn, Cd, Hg are not considered transition elements (full d-subshell).*

Atomic Radii

Decreases from Sc to Mn, stays constant for Fe, Co, Ni, and slightly increases for Cu, Zn.

Zr \(\approx\) Hf similarity due to Lanthanoid Contraction.

2. Magnetic & Spectral Properties

Magnetic Moment (\(\mu\)):

\[ \mu = \sqrt{n(n+2)} \text{ B.M.} \]

\(n\) = Number of unpaired electrons. B.M. = Bohr Magneton.

Color in Ions

Due to d-d transitions. Requires unpaired electrons.
• \(Sc^{3+}, Ti^{4+}\) (d\(^0\)): Colorless
• \(Zn^{2+}, Cu^+\) (d\(^{10}\)): Colorless

Catalytic Nature

Due to variable oxidation states and large surface area.
• Haber Process: \(Fe\)
• Contact Process: \(V_2O_5\)

3. Potassium Dichromate & Permanganate

Chromate-Dichromate Equilibrium:

\[ 2CrO_4^{2-} \text{ (Yellow)} + 2H^+ \rightleftharpoons Cr_2O_7^{2-} \text{ (Orange)} + H_2O \]

Low pH \(\to\) Orange | High pH \(\to\) Yellow

Compound	Acidic n-factor	Neutral/Weak Basic n-factor
\(KMnO_4\)	5 (\(Mn^{2+}\))	3 (\(MnO_2\))
\(K_2Cr_2O_7\)	6 (\(2Cr^{3+}\))	-

4. f-block Elements (Lanthanoids & Actinoids)

Lanthanoid Contraction:

Cause:

Poor shielding effect of 4f-electrons leads to a steady decrease in atomic and ionic radii with increasing atomic number.

Consequences:

Similarity in 4d and 5d series radii (\(Zr \approx Hf\), \(Nb \approx Ta\)).
Difficulty in separation of Lanthanoids.
Decrease in basic strength: \(La(OH)_3 > Lu(OH)_3\).

5. Comparative Study

Feature	Lanthanoids (4f)	Actinoids (5f)
Oxidation States	Mostly +3 (+2, +4 rare)	Wide range (higher OS up to +7)
Radioactivity	Only Promethium (\(Pm\))	All are Radioactive
Oxo-cations	Do not form	Form \(UO_2^{2+}, PuO_2^{2+}\), etc.

Mnemonic for Lanthanoids: Cerium (\(Ce\)) to Lutetium (\(Lu\)). Most stable oxidation state is +3.

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