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d- and f-Block Elements: one-page cheat sheet

NEET Chemistry · Unit 11 · Inorganic Chemistry

ScoreChemby CSJ Sir
Weightage: 3–4 questions · 12–16 marks

1 · Transition elements

Definitionpartly filled

d

-orbitals in the atom or in a common ion

Not typicalZn, Cd, Hg (

d^{10}

always)

(n - 1) d^{1 - 10} n s^{1 - 2}

ExceptionsCr

3 d^{5} 4 s^{1}

; Cu

3 d^{10} 4 s^{1}

Ions

4 s

electrons leave before

3 d

2 · Physical trends

Radiusfalls Sc to Cr, flat Fe to Ni, small rise Cu, Zn

m.p.peak near

d^{5}

(Cr); Mn dips; Zn, Cd, Hg low (Hg liquid)

d

≈ 5

d

equal radii from lanthanoid contraction

Causemetallic bonding by

n s

and unpaired

(n - 1) d

electrons

3 · Oxidation states & $E^{\circ}$

Lowestnumber of

s

electrons

Highest

s + d

electrons, up to Mn (+7)

Down a grouphigher states become more stable (Mo, W vs Cr)

Couple	$E^{\circ}$ (V)
Cr $^{3 +}$ /Cr $^{2 +}$	$- 0.41$
Fe $^{3 +}$ /Fe $^{2 +}$	$+ 0.77$
Mn $^{3 +}$ /Mn $^{2 +}$	$+ 1.57$
Cu $^{2 +}$ /Cu	$+ 0.34$

Mn $^{3 +}$ is a strong oxidant: it gains the stable $d^{5}$ . Cr $^{2 +}$ is a reductant: it gains $t_{2 g}^{3}$ in Cr $^{3 +}$ .

4 · Magnetism & colour

μ = n (n + 2) BM

$n$	$μ$ (BM)	Ions
1	1.73	Ti $^{3 +}$ , Cu $^{2 +}$
2	2.84	Ti $^{2 +}$ , Ni $^{2 +}$
3	3.87	V $^{2 +}$ , Cr $^{3 +}$
4	4.90	Cr $^{2 +}$ , Fe $^{2 +}$
5	5.92	Mn $^{2 +}$ , Fe $^{3 +}$

Colour

d

–

d

transition;

d^{0}

and

d^{10}

are colourless (Sc

^{3 +}

, Zn

^{2 +}

)

5 · Catalysts

Catalyst	Process
V $_{2}$ O $_{5}$	Contact process
Fe	Haber process
Ni	hydrogenation
PdCl $_{2}$	Wacker (ethene to ethanal)
TiCl $_{4}$ + Al(C $_{2}$ H $_{5}$ ) $_{3}$	Ziegler–Natta

6 · Potassium dichromate

Step 1roast chromite FeCr

_{2}

_{4}

with Na

_{2}

_{3}

and air: Na

_{2}

CrO

_{4}

(yellow)

Step 22CrO

_{4}^{2 -}

+ 2H

^{+}

\to

_{2}

_{7}^{2 -}

+ H

_{2}

O (yellow to orange)

Step 3Na

_{2}

_{2}

_{7}

+ 2KCl

\to

_{2}

_{2}

_{7}

+ 2NaCl

Cr_{2} O_{7}^{2 -} + 14 H^{+} + 6 e^{-} \to 2 Cr^{3 +} + 7 H_{2} O

Oxidises Fe $^{2 +}$ , I $^{-}$ , H $_{2}$ S; orange turns green. Structure: two tetrahedra sharing a corner, Cr–O–Cr 126°.

7 · Potassium permanganate

Prep.2MnO

_{2}

+ 4KOH + O

_{2}

\to

_{2}

MnO

_{4}

+ 2H

_{2}

Disprop.3MnO

_{4}^{2 -}

+ 4H

^{+}

\to

2MnO

_{4}^{-}

+ MnO

_{2}

+ 2H

_{2}

Medium	Product	$e^{-}$
Acidic	Mn $^{2 +}$	5
Neutral / weak alkaline	MnO $_{2}$	3
Strong alkaline	MnO $_{4}^{2 -}$	1

Equivalent mass $= M /5$ , $M /3$ , $M /1$ . MnO $_{4}^{-}$ is purple ( $d^{0}$ , charge transfer).

8 · f-Block

	Lanthanoids	Actinoids
Filling	$4 f$ ( $Z$ 58–71)	$5 f$ ( $Z$ 90–103)
Main state	+3	+3 and higher (+4 to +7)
Shielding	$4 f$ poor, buried	$5 f$ extends further
Radioactive	only Pm	all

^{4 +}

4 f^{0}

; also Eu

^{2 +}

(

f^{7}

), Yb

^{2 +}

(

f^{14}

), Tb

^{4 +}

(

f^{7}

)

Contractionpoor

4 f

shielding: basicity falls La to Lu

Seen in NEET 2026

Spin-only $μ$ of Ti $^{2 +}$ ( $3 d^{2}$ ).

μ = 2 (2 + 2) = 2.84 BM

Seen in NEET 2022

KMnO $_{4}$ oxidises I $^{-}$ to IO $_{3}^{-}$ in neutral medium. Change in Mn?

MnO $_{4}^{-}$ to MnO $_{2}$ : +7 to +4.

Seen in NEET 2024

Why is $E^{\circ}$ (Mn $^{3 +}$ /Mn $^{2 +}$ ) $= + 1.57$ V so positive?

Mn $^{3 +}$ ( $d^{4}$ ) gains an electron to reach the half-filled $d^{5}$ of Mn $^{2 +}$ .

Seen in NEET 2025

Strictly diamagnetic lanthanoid ions?

Ce $^{4 +}$ ( $4 f^{0}$ ) and Yb $^{2 +}$ ( $4 f^{14}$ ): no unpaired electrons.

Also in NEET 2022

Gd ( $4 f^{7} 5 d^{1} 6 s^{2}$ ) has a low third ionisation enthalpy: removing the $5 d$ electron leaves stable $4 f^{7}$ .

Six traps to remember

Zn, Cd and Hg are not true transition elements ( $d^{10}$ ).
Cr is $3 d^{5} 4 s^{1}$ and Cu is $3 d^{10} 4 s^{1}$ , not $4 s^{2}$ .
Cr $^{2 +}$ and Fe $^{2 +}$ both have 4 unpaired electrons: $μ = 4.90$ BM.
Mn $^{3 +}$ /Mn $^{2 +}$ is $+ 1.57$ V because $d^{4} \to d^{5}$ is favoured.
KMnO $_{4}$ : 5 electrons in acid, 3 in neutral or weakly alkaline medium.
Ce $^{4 +}$ is stable as $4 f^{0}$ ; Gd has a low third ionisation enthalpy for $4 f^{7}$ .

d- and f-Block Elements: free one-page cheat sheet

1 · Transition elements

2 · Physical trends

3 · Oxidation states & E∘

4 · Magnetism & colour

5 · Catalysts

6 · Potassium dichromate

7 · Potassium permanganate

8 · f-Block

Seen in NEET 2026

Seen in NEET 2022

Seen in NEET 2024

Seen in NEET 2025

Also in NEET 2022

Six traps to remember

3 · Oxidation states & $E^{\circ}$