Misconception 1: "All transition metals are coloured."

• Reality: Transition metal ions are coloured only when the d-subshell is partially filled ($d^{1}$ to $d^{9}$). $Sc^{3+}$ ($d^{0}$) and $Zn^{2+}$ ($d^{10}$) are colourless because d–d transitions are impossible.

Misconception 2: "Electronegativity determines ligand field strength."

• Reality: $F^{-}$ (most electronegative) is a weak field ligand. Field strength depends on σ-donor and π-acceptor ability. $CN^{-}$ and CO are strong field because they are σ-donors and π-acceptors (back-bonding increases $\Delta o$).

Misconception 3: "The coordination number is always 6."

• Reality: CN can be 2 (linear, e.g. [Ag($NH_{3}$){2}]^{+}), 4 (tetrahedral [$NiCl_{4}$]^{2-} or square planar [Pt($NH_{3}$){2}$Cl_{2}$]), or 6 (octahedral). It depends on the metal ion's size and the ligands.

Misconception 4: "Lanthanoids show +3 and +4 only."

• Reality: Lanthanoids predominantly show +3. Ce also shows +4, Eu shows +2, Sm shows +2 in some cases. The +3 state is overwhelmingly dominant because the 4f orbitals contract sharply beyond Ce.

Misconception 5: "Ionisation isomers have different molecular formulas."

• Reality: Ionisation isomers have the SAME molecular formula. The difference is which anion is inside the coordination sphere (as a ligand) and which is outside (as a counter-ion). Example: [Co($NH_{3}$){5}Br]$SO_{4}$ vs [Co($NH_{3}$){5}$SO_{4}$]Br — same formula $C_{5}H_{15}N_{5}BrO_{4}SCo$.

Misconception 6: "$\Delta t$ = $\Delta o$ for tetrahedral complexes."

• Reality: $\Delta t$ ≈ 4/9 $\Delta o$. The factor 4/9 arises from geometry (4 ligands approaching between axes, not along them).

Misconception 7: "All actinoids are man-made."

• Reality: Only transuranium elements (Z > 92) are man-made. Th, Pa, U are naturally occurring actinoids (in trace amounts in Earth's crust).