Chemical Bonding

Cheat Sheet  ·  Chemistry Gr 11
Emil Oliversen
BOND TYPES
BondAtomsMechanismΔEN
Ionicmetal + nonmetale⁻ transfer>1.7
Polar cov.nonmetal + nonmetalunequal share0.5–1.7
Nonpolar cov.nonmetal + nonmetalequal share<0.5
Metallicmetal + metale⁻ sea—
BOND STRENGTH & LENGTH
Strength
ionic > triple > double > single
Length
triple < double < single
More bonds = shorter and stronger.
IONIC PROPERTIES
  • High melting point (strong lattice)
  • Brittle — layers repel if shifted
  • Conducts when molten or dissolved
  • No conduction as solid (locked ions)
Lattice energy ↑ with higher charges and smaller ions (MgO > NaCl).
METALLIC BONDING
  • Sea of delocalized electrons
  • Conductive — e⁻ flow freely
  • Malleable — layers slide, e⁻ readjust
  • Lustrous — e⁻ reflect light
LEWIS STRUCTURES — STEPS
  1. Count total valence e⁻ (add 1 per − charge; subtract 1 per + charge)
  2. Draw skeleton — least EN atom in centre (H always terminal)
  3. Place octets on outer atoms first (duet for H)
  4. Put remaining e⁻ on central atom as lone pairs
  5. Form multiple bonds if central atom still needs e⁻
Formal charge
Ve⁻ − LP e⁻ − ½(bond e⁻)
Best structure: formal charges closest to 0. Neg. FC on most EN atom.
KEY EXAMPLES
MoleculeVe⁻BondsLP on central
H₂O82 single2 lone pairs
NH₃83 single1 lone pair
CO₂162 double0 lone pairs
N₂101 triple1 LP each N
HCl81 single3 LP on Cl
VALENCE ELECTRONS (common)
Group 1
1 Ve⁻ (Na, K, Li…)
Group 2
2 Ve⁻ (Mg, Ca, Be…)
Group 14
4 Ve⁻ (C, Si…)
Group 15
5 Ve⁻ (N, P…)
Group 16
6 Ve⁻ (O, S…)
Group 17
7 Ve⁻ (F, Cl, Br…)
VSEPR GEOMETRY
Count ALL e⁻ groups (bonding + lone pairs). Lone pairs compress angles.
e⁻ groupsLPShapeAngleExample
20Linear180°CO₂
30Trig. planar120°BF₃
40Tetrahedral109.5°CH₄
41Trig. pyramidal~107°NH₃
42Bent~104.5°H₂O
Angle trend: 109.5° (tetrahedral) → 107° (NH₃, 1 LP) → 104.5° (H₂O, 2 LP). Each lone pair compresses angles further.
KEY VSEPR WORKED CASES
CH₄
4 bonds, 0 LP → tetrahedral 109.5°
NH₃
3 bonds, 1 LP → trig. pyramidal 107°
H₂O
2 bonds, 2 LP → bent 104.5°
CO₂
2 double bonds, 0 LP → linear 180°
BF₃
3 bonds, 0 LP → trig. planar 120°
Remember: a double/triple bond = ONE electron group for VSEPR counting.
POLARITY
Bond polarity: ΔEN determines if a bond is polar. Molecular polarity: depends on shape too.
ΔEN < 0.5
nonpolar covalent
ΔEN 0.5–1.7
polar covalent
ΔEN > 1.7
ionic
MOLECULAR POLARITY EXAMPLES
MoleculeShapePolar?Why
H₂OBentYesAsymmetric → dipoles add
CO₂LinearNoSymmetric → dipoles cancel
NH₃Trig. pyr.YesAsymmetric shape
CCl₄TetrahedralNoSymmetric → dipoles cancel
CHCl₃TetrahedralYesH≠Cl → asymmetric
BF₃Trig. planarNoSymmetric → dipoles cancel
COMMON MISTAKES
  • Lone pairs ARE e⁻ groups — they affect shape
  • Double/triple bond = ONE e⁻ group in VSEPR
  • CO₂ has polar bonds but is nonpolar overall
  • Bond polarity ≠ molecular polarity
  • Ionic compounds only conduct when molten or dissolved, not as solid
  • Formal charges must sum to overall charge of molecule
ELECTRONEGATIVITY (PAULING)
F
3.98 (highest)
O
3.44
N / Cl
3.04 / 3.16
C / H
2.55 / 2.20
Na / Mg
0.93 / 1.31