Mistake: Confusing electron geometry with molecular shape. Correct: $XeF_{2}$ has 5 electron pairs (TBP electron geometry) but the molecular shape is LINEAR because the two F atoms are in axial positions. Always report the molecular shape (ignoring lone pairs), not the electron geometry.

Mistake: Thinking symmetric-looking molecules always have μ = 0. Correct: $NF_{3}$ looks symmetric but has μ ≠ 0 because the lone pair on N contributes to the net dipole. $BF_{3}$ has μ = 0 because it is truly trigonal planar with no lone pair.

Mistake: Using the same MO filling order for all diatomics. Correct: $B_{2}$, $C_{2}$, $N_{2}$ (Z ≤ 7) have π2p BELOW σ2p (mixing). $O_{2}$, $F_{2}$ (Z > 7) have the normal order (σ2p below π2p). Applying $O_{2}$'s order to $N_{2}$ will give wrong bond order and magnetic character.

Mistake: Forgetting that $O_{2}$ is paramagnetic. Correct: VBT predicts $O_{2}$ as diamagnetic (incorrect). MOT correctly shows 2 unpaired electrons in the two degenerate π*2p orbitals. This is the most tested fact about MOT in NEET.

Mistake: Counting pi bonds when calculating steric number. Correct: Only sigma bonds and lone pairs count for the steric number. Each single bond = 1σ; each double bond = 1σ (ignore the π); each triple bond = 1σ (ignore the 2π). This determines hybridization.

Mistake: Applying Born-Haber cycle with wrong sign for EA. Correct: Electron affinity (EA) for most halogens is exothermic (negative). When plugging into $\Delta H$_f = $\Delta H$_sub + IE + ½$\Delta H$_diss + EA + U, use the actual signed value. A sign error on EA or lattice energy U is the most common numerical error.

Mistake: Treating the $CHCl_{3}$ vs $CCl_{4}$ dipole question wrong. Correct: $CCl_{4}$ is tetrahedral and symmetric → μ = 0. $CHCl_{3}$ has three C–Cl dipoles pointing in similar directions (C–H is much less polar) → net μ ≠ 0. Always check whether ALL bonds are identical and symmetric.