Cheat Sheet — Everything Testable in INC-04 — Notes

Configuration Anomalies

Cr = $[\text{Ar}]\, 3d^5\, 4s^1$ (half-filled d → exchange energy)
Cu = $[\text{Ar}]\, 3$d^{10}$\, 4s^1$ (fully-filled d → stability)

$KMnO_{4}$ Products

Medium	Product	Colour	$e^{-}$ Gained
Acidic	$Mn^{2+}$	Colourless	5
Neutral	$MnO_{2}$	Brown ppt	3
Basic	$MnO_{4}^{2-}$	Green	1

Chromate-Dichromate

$CrO_{4}^{2-}$ (yellow) in basic ⇌ $Cr_{2}O_{7}^{2-}$ (orange) in acidic
$K_{2}Cr_{2}O_{7}$ in acid: $Cr^{6+}$ → $Cr^{3+}$ (orange → green)

Spectrochemical Series (Weak → Strong)

$\text{I}^- < \text{Br}^- < \text{Cl}^- < \text{F}^- < \text{OH}^- < \text{H}_2\text{O} < \text{NH}_3 < \text{en} < \text{NO}_2^- < \text{CN}^- < \text{CO}$

CFT Summary

Parameter	Octahedral	Tetrahedral
Lower set	t_{2}g	e
Higher set	eg	t_{2}
Splitting	$\Delta o$	$\Delta t$ = 4/9 $\Delta o$
Usual spin	Low or high	Almost always high

Magnetic Moment

$\mu = \sqrt{n(n+2)}\text{ BM}$

Isomerism Types

Type	Trigger
Geometrical	$MA_{2}B_{2}$ (sq. planar) or $MA_{4}B_{2}$ (octahedral)
Optical	Chelate complexes, no symmetry plane
Linkage	Ambidentate ligands ( $NO_{2}^{-}$ , S $CN^{-}$ )
Ionisation	Ligand-counter ion exchange

Biological Coordination Compounds

$Fe^{2+}$ → Hemoglobin | $Mg^{2+}$ → Chlorophyll | $Co^{3+}$ → Vitamin $B_{12}$ | $Zn^{2+}$ → Carbonic anhydrase

Lanthanoid Contraction

$La^{3+}$ (116 pm) → $Lu^{3+}$ (85 pm): gradual shrinkage
Cause: poor 4f shielding → increasing Z_eff
Consequence: Zr ≈ Hf in size (hardest pair to separate)

IUPAC Naming Order

Ligands (alphabetical) → Metal name → (Oxidation state) → External ion

Anionic complexes: metal root + -ate (ferrate, cobaltate, platinate)
Anionic ligands: suffix -o (chlorido, cyanido, hydroxido, oxalato)
Neutral exceptions: aqua, ammine, carbonyl, nitrosyl

Werner's Theory

Primary valence = oxidation state = ionisable
Secondary valence = coordination number = non-ionisable, directional