d and f Block Elements and Coordination Compounds formulas for JEE Main & Advanced

10 formula entries for d and f Block Elements and Coordination Compounds, in the order the chapter builds them. Each shows the formula, when to use it and the first trap to avoid.

General Electronic Configuration of d-Block Elements

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

When to use. When determining electronic configuration of transition metals or predicting their properties.

Trap. Forgetting that Cr is 3d⁵4s¹, not 3d⁴4s².

Magnetic Moment Formula

μ = \sqrt{n (n + 2)} BM

When to use. Calculating magnetic moment from number of unpaired electrons or vice versa, especially for transition metal complexes.

Trap. Using n as total electrons instead of unpaired electrons.

Color of Transition Metal Complexes

Δ_{oct} = energy of d-d transition

When to use. Explaining or predicting color of transition metal ions/complexes based on oxidation state and ligand.

Trap. Assuming all transition metal compounds are colored; Sc³⁺ and Ti⁴⁺ are colorless due to d⁰ configuration.

Crystal Field Splitting Energy (CFSE) for Octahedral Complexes

CFSE = (- 0.4 Δ_{o} \times n_{t_{2 g}}) + (0.6 Δ_{o} \times n_{e_{g}})

When to use. Calculating stabilization energy to predict geometry, spin state, or magnetic properties.

Trap. Forgetting to account for pairing energy in low-spin complexes.

Effective Atomic Number (EAN)

EAN = Z_{metal} - oxidation state + 2 \times coordination number

When to use. Predicting stability of metal carbonyls or organometallic complexes.

Trap. Forgetting to subtract oxidation state first.

Stability Constant (K_f) and Instability Constant (K_d)

K_{f} = \frac{[M L_{n}]}{[M] [L]^{n}}

When to use. Comparing stability of complexes or predicting displacement reactions.

Trap. Confusing K_f with K_d; they are reciprocals.

Magnetic Properties of Coordination Compounds

μ = \sqrt{n (n + 2)} BM

When to use. Predicting magnetic behavior from electronic configuration and ligand field strength.

Trap. Assuming all transition metal complexes are paramagnetic; d⁰ and d¹⁰ are diamagnetic.

Crystal Field Splitting in Tetrahedral Complexes

Δ_{t} = \frac{4}{9} Δ_{o}

When to use. Predicting geometry and spin state for tetrahedral complexes like [CoCl₄]²⁻.

Trap. Using octahedral splitting energy for tetrahedral calculations.

Important Reactions of d-Block Elements

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

When to use. Solving redox reactions and qualitative analysis problems.

Trap. Forgetting color changes: Cr₂O₇²⁻ orange, Cr³⁺ green/violet.

Applications of Coordination Compounds

4 Au + 8 {CN}^{-} + O_{2} + 2 H_{2} O \to 4 [{Au(CN)}_{2}]^{-} + 4 {OH}^{-}

When to use. Connecting coordination chemistry to real-world applications.

Trap. Thinking EDTA only used in water softening; it's also used in medicine for heavy metal poisoning.

Values to remember

$Cr: 3 d^{5} 4 s^{1}$ General Electronic Configuration of d-Block Elements
$Cu: 3 d^{10} 4 s^{1}$ General Electronic Configuration of d-Block Elements
$BM = 9.27 \times 10^{- 24} {J T}^{- 1}$ Magnetic Moment Formula
$Mn: +2, +4, +6, +7$ Oxidation States of d-Block Elements
$Cr: +2, +3, +6$ Oxidation States of d-Block Elements
$Δ_{o} for typical ligands: H_{2} O < {NH}_{3} < {CN}^{-}$ Crystal Field Splitting Energy (CFSE) for Octahedral Complexes
$Fe: 26, Co: 27, Ni: 28$ Effective Atomic Number (EAN)
$Weak: H_{2} O, F^{-}$ Spectrochemical Series
$Strong: {CN}^{-}, CO$ Spectrochemical Series
$Lanthanoids: 4 f^{1} to 4 f^{14}$ f-Block Elements: Lanthanoids and Actinoids
$Actinoids: 5 f^{1} to 5 f^{14}$ f-Block Elements: Lanthanoids and Actinoids
${KMnO}_{4} in acid: {Mn}^{2 +}$ Important Reactions of d-Block Elements
$K_{2} {Cr}_{2} O_{7} in acid: {Cr}^{3 +}$ Important Reactions of d-Block Elements

Read the full chapter: d and f Block Elements and Coordination Compounds for JEE, with what JEE asks and the common traps.