Maharashtra State Board · Class 12 · Chemistry · Chapter 9

Coordination Compounds — Formula Sheet

Board Formulas

11 formulas

1.Werner's Primary and Secondary Valency★
$Primary = ionisable (satisfies charge), Secondary = coordination number$
Primary valency ⇌ oxidation state; secondary valency ⇌ coordination number.
2.Coordination Number
$C N = number of ligand donor atoms bonded to central metal$
Common CNs: 2 (linear), 4 (tetrahedral/square planar), 6 (octahedral).
3.Charge on Complex Ion
$Q_{co m pl e x} = Q_{m e t a l} + \sum Q_{l i g an d s}$
Neutral ligands don't add charge; anionic ligands add their negative charge.
4.Ligand Notation Priority (IUPAC)
$alphabetical order in name; anionic prefix - o (chlorido, cyanido, sulfato)$
Neutral: aqua, ammine, carbonyl, nitrosyl. Cationic: −ium suffix.
5.Crystal Field Splitting — Octahedral★
$Δ_{o} = E (e_{g}) - E (t_{2 g})$
d-orbitals split: t2g (lower, 3 orbitals) and eg (higher, 2 orbitals). Δ_o depends on ligand strength.
6.Crystal Field Splitting — Tetrahedral★
$Δ_{t} = \frac{4}{9} Δ_{o}$
For same metal and ligand. Tetrahedral splitting is smaller and pairing rarely occurs.
7.Crystal Field Stabilization Energy (CFSE)
$CFSE = (- 0.4 n_{t_{2 g}} + 0.6 n_{e_{g}}) Δ_{o}$
Sum electron contributions in Δ_o units. Ignore pairing energy in this simple form.
8.Magnetic Moment (spin only)★
$μ = n (n + 2) BM$
n = number of unpaired electrons. BM = Bohr magneton.
9.Effective Atomic Number (EAN)
$EAN = Z - Q_{o x} + 2 \times C N$
Sidgwick's rule. Stable complexes often have EAN = noble-gas configuration.
10.Spectrochemical Series (ligand strength)
$I^{-} < B r^{-} < C l^{-} < F^{-} < O H^{-} < H_{2} O < N H_{3} < e n < C N^{-} < C O$
Strong field ligands (CN⁻, CO) → large Δ_o → low-spin. Weak field → small Δ_o → high-spin.
11.Low-Spin vs High-Spin Condition
$High-spin: Δ_{o} < P; Low-spin: Δ_{o} > P$
P = pairing energy. Compare Δ_o with P to predict spin state.