Chemical Bonding & Molecular Structure — Visual Guide — Summary

Concept Map: Bonding Framework

VSEPR Shape Decision Table

Lone Pairs on Central Atom	SN=4 Shape	SN=5 Shape	SN=6 Shape
0	Tetrahedral (109.5°)	Trigonal bipyramidal	Octahedral (90°)
1	Trigonal pyramidal (~107°) ↓	See-saw (~90°/120°) ↓	Square pyramidal (~90°) ↓
2	Bent (~104.5°) ↓↓	T-shape (~90°) ↓↓	Square planar (90°) ↓↓
3	—	Linear (180°) ↓↓↓	—

(↓ = bond angle compressed relative to ideal by lone pair repulsion)

MO Energy Level Comparison

Feature	Z ≤ 7 ( $B_{2}$ , $C_{2}$ , $N_{2}$ )	Z > 7 ( $O_{2}$ , $F_{2}$ )
2p MO order	π2p below σ2p	σ2p below π2p
Key difference	π2p fills first (mixing) ↑	σ2p fills first (normal) ↑
Affected BO	$N_{2}$ BO = 3 (correct only with mixing order)	$O_{2}$ BO = 2
Magnetism	$N_{2}$ diamagnetic	$O_{2}$ paramagnetic

Dipole Moment: Zero vs Non-Zero

μ = 0 (symmetric)	μ ≠ 0 (asymmetric or lone pair)
C $O_{2}$ — linear	$H_{2}O$ — bent (lone pairs)
$BF_{3}$ — trigonal planar	$NH_{3}$ — pyramidal (lone pair)
$CCl_{4}$ — tetrahedral	$CHCl_{3}$ — tetrahedral but asymmetric bonds
$SF_{6}$ — octahedral	S $O_{2}$ — bent (lone pair)

Born-Haber Cycle for NaCl (Energy Ladder)

Na(g) + ½$Cl_{2}$(g)  ──(+121 kJ ½$\Delta Hd$iss)──►  Na(g) + Cl(g)
     ↑ +108 kJ (sublimation)                      ↓ −349 kJ (EA)
Na(s) + ½$Cl_{2}$(g)                            $Na^{+}$(g) + $Cl^{-}$(g)
     ↑ $\Delta Hf$ = −411 kJ                               ↓ U = −787 kJ
          Na(s) + ½$Cl_{2}$(g) ←──────── NaCl(s)

$U = \Delta H_f - \Delta H_{sub} - \frac{1}{2}\Delta H_{diss} - IE - EA = -787 \text{ kJ/mol}$